After graduating, she returned to China and taught at Yanjing University, where she went to the University of Berlin, Germany in 1933 to conduct research on rayon and invented the first rayon made from grass fibres, returning to China in 1936 to serve as a commissioner of the Central Economic Commission. In 1938 she moved to Chongqing to set up the Southwest Chemical Industry Manufacturing Factory, where she conducted research on ramie processing and eventually spun out the "Cloud Silk", known as Yunsi fiber. In 1949, she attended the First Plenary Session of the Chinese People's Political Consultative Conference.
After the founding of the Peoples Republic of China, Feng Yunhe became an advisor to the Ministry of Textile Industry and Deputy Director of the Guangdong Chemical Research Institute, and in 1951, she began researching the chemical denaturation of ramie fibres, which was successful after five years of experiments. During the Cultural Revolution, she was branded as a "reactionary academic authority". After the end of the Cultural Revolution, she became a consultant to the Shanghai Textile Industry Bureaus Wool and Hemp Textile Industry Company and joined the Communist Party of China in 1979. She was awarded the invention prize by the State Science and Technology Commission in 1981 for the development of a large number of ramie fibre sulphonation denaturation products in Shanghai, and was a technical advisor to Hubei Province on textile technology from 1984.