From 1915 to 1919 she held a position as principal of the Women's Normal College in Mukden, but she returned to England in 1919.

[1][2] Whilst teaching full-time at SOAS she also studied as an external student at the University of London, and obtained a BA (first class) in Chinese in 1924, and then an MA (with distinction) in 1925.

[2] In October 1934 Johnston wrote to Charles Otto Blagden, then Dean of SOAS, stating that if the school was unable to support both a professor and a reader of Chinese then he would not object to his position not being renewed.

She wrote a popular study of Confucius in 1940, and edited anthologies of translations under the titles Dragon Book (1938) and Bamboo, Lotus and Palm (1948).

[1] In addition to her academic studies, she played an important role in the administration of the Far East Department at SOAS, and organizing the running of Chinese, Japanese and Malay language courses during the Second World War.