The son of Qin Shi Huang, he was put on the throne by Li Si and Zhao Gao, circumventing his brother Fusu, who had been the designated heir.

Upon Huhai's ascension, both Fusu and the popular general Meng Tian were killed on the orders of Li and Zhao, with Qin Er Shi's role in the assassinations remaining uncertain and controversial.

A weak ruler, Qin Er Shi's reign was completely dominated by Zhao Gao, who eventually forced him to commit suicide.

[3][4] By the time of his death, the Qin Empire's power had lessened so much that his successor Ziying ruled as a king, not emperor.

[8][9] From an early age, Huhai was apprenticed to the minister Zhao Gao to learn Legalism, by the decree of Qin Shi Huang.

There is a possibility that Hu Ji was a princess from the Greco-Bactrian Euthydemid dynasty offered to Ying Zheng as an alliance gift from neighboring Gansu in 230 BC.

[10] Qin Shi Huang died during one of his tours of eastern China in the summer of 210 BC at the palace in Shaqiu.

[11][12] The announcement of his death was withheld until the entourage, which was accompanied by Premier Li Si and the imperial court, returned to the capital, Xianyang, two months later.

[11] Nevertheless, Huhai and Zhao Gao were aware of Qin Shi Huang's death and began plotting an internal intrigue.

[13] Li Si and Zhao Gao forged a fake edict by Qin Shi Huang ordering both Fusu and Meng to commit suicide.

[13] Their plan worked, and the younger son, Huhai, acceded the throne to become the second emperor, later known as Qin Er Shi.

[11] However, recent findings of bamboo strips dating from the time of the intrigue note that Huhai was elected and killed his brother.

After one of the tours, Zhao Gao suggested for him to examine the governors and military commandants and to punish those guilty of some crime.

Military leaders such as Chen Sheng delegitimized the rule of Qin Er Shi by claiming Fusu should have been made ruler.

[7][19] Zhao Gao continued to push the emperor to find associates with loyalty and to punish those who showed disloyalty with more severe penalties.

[7] This incident provides the modern Chinese chengyu "point to a deer and call it a horse" (指鹿為馬 zhǐlù wéimǎ);.

Surrounded and with no means of escape, Qin Er Shi asked the loyal eunuch why he had not told the truth earlier.

Qin Er Shi reigned only for three years and was forced to commit suicide eventually by Zhao Gao at the age of 22.