Moinfar was born in Tehran in May 1928. He graduated with a structural engineering degree from Tehran University in 1951. He furthered his studies in seismic engineering under professor Seiji Naito in Weseda university Japan. He was a founding member of the Islamic Association of Engineers.
Moinfar worked at the plan and budget organization during the reign of Shah Mohammad Reza Pahlavi. He had connections with the Freedom of Iran movement, which was led by Mehdi Bazargan. However, this link was not formal and he never attached himself to the movement.
Following the 1979 revolution, Moinfar became one of the members of the Revolutionary Council. He also acted as the spokesman of the council. He was named minister of budget and planning to the interim government headed by Mehdi Bazargan.
In September 1979, Moinfar was appointed oil minister in a cabinet reshuffle, becoming the first oil minister of Iran in September 1979, when the office was established. He was also appointed chairman and managing director of the National Iranian Oil Company (NIOC), replacing Hasan Nazih.
Moinfar continued to serve as oil minister after the resignation of the interim government of Bazargan in November 1979. He also won a parliamentary seat in the 1980 general elections. However, he was harshly criticized by the fundamentalists for removing ‘only committed Moslems’ rather than leftists from the ministry. Moinfar's tenure lasted until September 1980 when Mohammad Ali Rajai formed the cabinet. Ashgar Ibrahimi was nominated to succeed Moinfar as oil minister. However, Ibrahimi did not get necessary vote at the Majlis, and Mohammad Javad Baqer Tondguyan became the oil minister.