Keynes was in the 1930s and 1940s, which was the period of economic recovery after the American economic crisis. Keynes believed that the effective demand composed of consumption demand and investment demand mainly depends on three basic psychological factors: consumption tendency, marginal efficiency of capital, liquidity preference and money quantity. Therefore, in Keynesian economic theory, financial theory occupies a very important position. It can even be said that Keynes's economic theory is based on his monetary and financial theory.