Born into a prominent family in Changshu, as a student in Shanghai he joined the Communist Party of China (CPC) during the May Thirtieth Movement in 1925, and became a key technical specialist in the early history of the CPC. After Chiang Kai-shek's Kuomintang (KMT) massacred the Communists in 1927, Li was recruited by Zhou Enlai as the communications head of Teke, the CPC's intelligence agency, and created the CPC's first underground radio station. After his close friend and colleague Gu Shunzhang defected to the KMT in 1931, Li was forced into exile in the Soviet Union, where he studied to become a radio expert and published a book on rhombic antenna.