In 1939, he joined the League in Defense of China sponsored and organized by Soong Ching Ling, in which he was in charge of publicity work. During the War of Resistance Against Japanese Aggression, when serving as a correspondent of the United Press and the Allied Labor News of the United States, Epstein visited North Shaanxi Province and Shanxi-Suiyuan Anti-Japanese Base Areas, and interviewed Mao Zedong, Zhou Enlai and other CPC leaders, along with a delegation of Chinese and foreign reporters.

In 1951, in response to the invitation of Soong Ching Ling, he returned to China to participate in the work of starting publication of "China Reconstruct" .

In 1957 he was granted China's citizenship. During his lifetime, he was standing committee member of the National Committee of the Chinese People's Political Consultative Conference (CPPCC), honorary editor-in-chief of the "China Today", former "China Reconstruct", vice-chairman of the International Council of the China Industry Cooperation Association and member of the China Welfare Council, etc. His major books include "From Opium War to Liberation," "The People's War," "The Unfinished Revolution in China" and "Tibet Transformed."