As Tuoba Si grew, he was said to be a wise and kind young man, whose actions were all in accordance with proper protocol.

Emperor Mingyuan, contrary to his father's dictatorial style, instituted a council of eight officials to advise him on all important decisions, with the intent to hear different opinions and then take informed actions.

At the time of Emperor Mingyuan's ascension to power, the paranoia and violence of Tuoba Gui's late reign had caused many problems within Northern Wei, with the officials described as idle and arrogant, the law as not properly enforced, crime so common that criminals would act in public without fear of repercussions, and many people too afraid to go outside in alleyways.

Like his father, a feature of Emperor Mingyuan's reign was the commissioning of construction projects to expand Pingcheng as a capital and general state infrastructure.

In 414, Emperor Mingyuan sent ambassadors to Later Qin, Northern Yan, Jin, and Rouran, to try to establish peaceful relationships.

How successful the Rouran mission was is harder to gauge, for although initially it appeared to be successful, by new year 415 the Rouran Khan Yujiulü Datan (郁久閭大檀) invaded, and Emperor Mingyuan was forced to respond, chasing Yujiulü Datan back to his territory, but when Emperor Mingyuan sent his advisor Daxi Jin (達奚斤) to pursue Yujiulü Datan, the Northern Wei forces ran into severe weather and suffered many casualties based on frostbite.

Emperor Mingyuan had always been fond of mysticism and divination, and also often asked Cui Hao to make predictions based on those texts, which often came true.

In 415, the northern regions of Northern Wei suffered a major famine, causing Emperor Mingyuan to consider moving the capital southward to Yecheng (鄴城, in modern Handan, Hebei), but at the advice of Cui Hao and the official Zhou Dan (周澹), who believed that such a move would quickly expose the actual numerical inferiority of the Xianbei to the Han, he kept the capital at Pingcheng, but also pursuant to Cui and Zhou's suggestion, moved a number of impoverished Xianbei to the modern Hebei region.

In 416, the Jin general Liu Yu launched a major attack on Later Qin, intending to destroy it.

As part of Liu Yu's force, a fleet commanded by the general Wang Zhongde (王仲德), approached Northern Wei's only main outpost south of the Yellow River, Huatai (滑台, in modern Anyang, Henan), the Northern Wei general Yuchi Jian (尉遲建), apprehensive of the Jin forces, abandoned Huatai and fled back north of the Yellow River.

Emperor Mingyuan executed Yuchi and then sent messengers to rebuke Liu Yu and Wang Zhongde, both of whom restated that the target was Later Qin, not Northern Wei, and that the city would be returned as soon as the campaign was over.

(However, Jin did not actually return Huatai, and Northern Wei would not have a major presence south of the Yellow River again until 422.)

Emperor Mingyuan summoned his council to consider whether to launch armies to try to stop Jin advances to try to save Later Qin.

However, Cui Hao opined that this would precisely make Northern Wei the target of Jin attacks, and Emperor Mingyuan partially agreed, but still sent some 100,000 men, commanded by Baba Song, to guard the northern bank of the Yellow River to prepare for battle.

Many former Jin officials who opposed Liu Yu who had taken refuge with Later Qin fled to Northern Wei, and Emperor Mingyuan further ordered that anyone who could save and deliver members of the Yao imperial clan to Pingcheng would be greatly rewarded.

The state saw plentiful harvests during this period, and experienced relative stability, and after 417 there were no popular uprisings for the rest of his reign.

As an example of this, a group of families had declared allegiance to Northern Wei upon Later Qin's destruction, and Emperor Mingyuan established the official Kou Zan (寇讚) in position to manage these people.

In 420, Emperor Mingyuan's wife Consort Yao died, and regretting that he could never give her the title in life, he posthumously honored her as an empress.

In 422, Emperor Mingyuan suffered a major illness, which is attributed to his taking of the popular alchemical drug Cold Food Powder for many years.

Meanwhile, Emperor Mingyuan also sent Yizhan Jian and the generals E Qing (娥清), Lü Dafei (閭大肥) and Pu Ji (普幾) east, capturing several commanderies in modern western Shandong.

However, while other cities in Song's Qing Province (青州, modern central and eastern Shandong) fell as well, the Northern Wei forces were unable to capture the capital of Qing Province, Dongyang (東陽, in modern Qingzhou, Shandong), and were eventually forced to withdraw after food supplies ran out and a large number of soldiers grew ill. Northern Wei forces also stalled in their siege of Hulao, defended by the capable Liu Song general Mao Dezu (毛德祖), but were meanwhile able to capture Luoyang and Xuchang (許昌, in modern Xuchang, Henan) in spring 423, cutting off the path of any Liu Song relief force for Hulao.