Abstract: Roosevelt's New Deal and Keynesian economic theories were born to deal with the economic crisis in the capitalist world. They had a similar theoretical framework which uphelp the ideal of governmental interference. However, the New Deal's emergency nature, its process and the specific period in which the New Deal was carried out all prove that the relationship between Keynesian economic theories and the New Deal is not that of theories and practice. It can only be said that some vestige of Keynesian economic theories is evident in the New Deal or the latter was influenced by the former. Actually, the implementation of the New Deal helped strengthen the systematization and enrich the doctrine of governmental interference of Keynesian economic theories. They influenced each other. The research on this issue is beneficial for us to have a deeper and objective understanding of the former U.S President and his New Deal.