Abstract: According to Irving Fisher's theory, the trading volume of commodity decides monetary demand, and money circulation velocity is an important variable, though the volume is difficult to estimate. However, monetary theories after I.Fisher hold that the monetary demand is decided by national income or gross domestic product with the assumption or testified premise that money circulation velocity is stable, but the monetary demand is far greater than national income or gross domestic product. According to the empirical data of the United States, Japan and the United Kingdom, money circulation velocity based on social trading turnover is inconstant, and responds rapidly to the changes in social trading turnover and monetary stock as an important mechanism of monetary equilibrium. It is necessary to reexpress a monetary theory to reflect the role of money circulation velocity, and to restate the mechanism of the influence of monetary supply stock on economy.

Key words: monetary theories, monetary demand, monetary supply, money circulation velocity