This paper aims to make an empirical analysis of Cobb Douglas production function using ordinary least square method based on the data from 1973 to 2019 in the United States. All the data was collected from Fred database. This paper has explored the share of capital in production and the share of labor in production. The results show that the share of labor in production is much higher than the share of capital in production, which suggests that the United States should pay more attention to the labor force. The summation of share of capital and labor in production is slightly higher than 1, which means that there is a phenomenon of increasing returns to scale in American economy.