His father Miao Daishu (苗殆庶) did serve as an official, but only reached the office of secretary general of Longmen County (龍門, in modern Yuncheng, Shanxi).
Miao Jinqing himself was known for studiousness in his youth, and he was able to pass the imperial examinations, allowing him to enter civil service.
Sometime during the reign of Emperor Ruizong's son Emperor Xuanzong, Miao Jinqing started his official career as the sheriff of Xiuwu County (修武, in modern Jiaozuo, Henan), and then served as the sheriff of Fengxian County (奉先, near the Tang capital Chang'an) – which, given its proximity to Chang'an, was considered a promotion.
For the faults of someone he was associated with – the historical accounts were not clear[4] – he was then demoted to be a census officer at Xu Prefecture (徐州, roughly modern Xuzhou, Jiangsu).
In 735, he was promoted within the civil service affairs ministry to the position of Libu Langzhong (吏部郎中), serving under the deputy ministers.
At that time, there was peace in the Tang realm, and it was said that in a typical year, over 10,000 men would arrive at Chang'an to undergo the imperial examinations.
Because there were so many examinees, Emperor Xuanzong often also selected officials from other ministries to assist Miao and Song, hoping that by doing so the examination process could be fair.
A former county magistrate, Su Xiaoyun (蘇孝慍), heard about this, and he reported this to his former superior, the general An Lushan, who then was much favored by Emperor Xuanzong.
Why speak further?Once Miao arrived at Huguan, he spent several days inviting the people of the county to feasts and also donated a major part of his salary to serve as an education fund for the young men.
He was later moved to serve as governor of Fufeng Commandery (扶風, roughly modern Baoji, Shaanxi) and created the Baron of Gaoping.
He later served as the minister of public works (工部尚書, Gongbu Shangshu) and the official in charge of the eastern capital Luoyang.
As Tang forces staged their counterattack in 757, Emperor Suzong advanced from Lingwu to Fengxiang (鳳翔, i.e., the capital of Fufeng Commandery).
Later in the year, after Tang forces recaptured Chang'an and Luoyang, Miao continued to serve as chancellor and the head of the examination bureau — now retitled Shizhong (侍中).
Those who commented about him compared to Hu Guang [(胡廣, a Han dynasty prime minister who was known for his carefulness)].In 762, Emperor Xuanzong died.
This time, Miao declined, citing his own old age and his belief that having a regent was inappropriate given the circumstances, and Emperor Daizong agreed.
He also met Miao regularly at Yanying Hall (延英殿) – a mode which set a precedent for later emperors and later ailing chancellors.