During the Battle of Changping in 260 BC, he succeeded Wang He as the commander of Qin army, and soon defeated Zhao army commanded by Zhao Kuo. Zhao army was split into two parts and its supply lines were cut off by Bai Qi. More than 400,000 Zhao soldiers, who surrendered after Zhao Kuo was shot down by Qin archers, was decided to be buried alive by Bai Qi.
In 257 BC, Qin had a defeat in Handan, capital of Zhao, the King of Qin ordered him to take over the army as a commander. Bai Qi, however, believed that it was not the correct time to attack Zhao, so he refused the command of the king with an excuse of his sickness. The Prime Minister of Qin, Fan Ju tried to persuade Bai Qi, but he failed. The king, therefore, had to use Wang Ling (王陵), another prominent military general of Qin, instead of Bai Qi, as the commander. Nevertheless, this decision did not help Qin army in the battle at all. After more than 5 months continuous defeat in Handan, the king asked Bai Qi to be the commander again. Bai Qi, who believed Qin cannot gain a victory in this battle, refused the request with the excuse of his sickness, once more. Having been refused several times, the King, who had become angry, removed all titles from Bai Qi and forced him to leave Xianyang, the capital of Qin. In addition, the prime minister of Qin, Fan Ju, feeling he had lost face by Bai Qi's refusals, made the King of Qin believe that Bai Qi would join another state as a general and become a threat to the State of Qin. Convinced by Fan Ju, the King of Qin then forced Bai Qi to commit suicide in Duyou (杜邮).