During the Japanese occupation, his Father migrated south to Guangzhou to work in a Kuomintang government arms factory as an accounts clerk. After 1949, his Father was appointed as the President of No. 1 Middle School of Duyun (Chinese: 都匀一中) where he met Ren Zhengfei's mother; the elder Ren became a member of the Communist Party in 1958. His mother was a senior Teacher at the No. 1 Middle School of Duyun.

After completing secondary school, Ren Zhengfei attended the Chongqing University in the 1960s, and then joined the People's Liberation Army (PLA) research institute to work as a military technologist reportedly in the PLA's Information Technology research unit. During his time in the PLA, Ren did not hold military rank. He was excluded from joining the Communist Party of China for most of his career in the military, due to his parents' social background and their ties to the Kuomintang. During this time, Ren was responsible for a number of Technology achievements that were recognized at various levels. For this reason, Ren was selected as a delegate from PLA to attend the National Science Conference in 1978. In 1982, Ren retired from the army due to a large PLA workforce reduction which impacted 500,000 active duty personnel. In 1983, after becoming a civilian, Ren moved to Shenzhen and worked in the electronics Business.

Ren retired from the People's Liberation Army as a civilian employee of a rank equivalent to a major in 1982. He joined the Communist Party of China in 1978. As a representative of private entrepreneurs, he was elected member of the 12th National Congress of the Communist Party of China. Among his other accomplishments, Ren is responsible for developing cooperative programs with businesses in China’s interior regions. Ren's ex-wife was the daughter of a Communist Politician who served at one time as deputy Governor of Sichuan Province.

In 1987, Ren founded Huawei Technologies Co. Ltd with 21,000 yuan, around US$ 5,000 at the time. Initially Huawei mostly sold telephone exchange equipment from Hong Kong.

Time Magazine included Ren Zhengfei in its list of 100 most influential people of 2005.

Ren holds 1.42% of the shares of Huawei, valued at US$450 million in 2010. Huawei is essentially independent of Ren because it is held by most of its employees, but the ownership structure remains opaque.

He now serves as a deputy chairman of the Board of Directors, but he is not among the current three rotating CEOs. The company had an annual revenue of 34 billion USD with 10% going into research & development, and over 144,000 employees as of January 2013.