[2] In 1922, Geng was a child worker in a lead-zinc mine in Shuikoushan, south of Hengyang City in China.

On 10 October 1934, he embarked on the Long March as the pioneer of 2nd division and, in the beginning of 1935, seized a critical military fortress at Loushanguan in Guizhou Province.

The Fourth Corps had just arrived in northern Shaanxi having been commanded by Zhang Guotao, and Geng took control of the unit.

His army occupied East Gansu Province, responsible for the safety of west border of Shaan-Gan-Ning Region.

[citation needed] In 1946, Geng accompanied Ye Jianying to participate in the Beiping Military Conciliatory Commission, initiated by General George C. Marshall to promote and prevent the outbreak of civil war between the Chinese Communists and Nationalists.

[citation needed] After the formation of People's Republic of China, Geng was appointed as the ambassador to Sweden, and minister to Denmark and Finland on 9 May 1950.

In 1978, he was appointed as vice-premier of the State Council, in charge of foreign relations, military industry, civil airlines and tourism.

In his final years, he was known for presenting the Geng Biao Question to cadres of the Party: "If one day you get sentenced, how far will the people you govern go to plead your case in an attempt to save you?"