The forecast of GDP has always been a popular research topic today, and its related influencing factors are also complicated. This paper selects three key factors in economic development: gold price, crude oil price, and stock market index, explores their relationship with U.S. GDP, and then uses these three factors as predictive variables to obtain a multiple linear regression equation related to GDP. The research methods of this paper are as follows: Firstly, monthly U.S. GDP, monthly crude oil price, monthly gold price, and monthly S&P 500 index were collected. Secondly, correlation analysis was carried out on these data, including calculation of correlation coefficient and cross-correlation analysis. Correlation analysis showed that GDP had a significant positive correlation with other variables. Then, a multiple linear regression model was established with monthly U.S. GDP as the predicted variable, monthly crude oil price, monthly gold price, and monthly S&P 500 index as the predictor variable. Finally, multiple regression equations are obtained through testing. This multiple regression equation can be used to predict GDP further.