The U.S. economy experienced cyclical slowdown early in 2015 while main fundamental indicators remain stable. Domestic consumption still drive the growth，however uncertainties of investment and external fluctuation overhung. The improving of labor market condition，elevating of the consumer confidence，increasing of personal disposal income and the contribution of government expenditure enhanced economic growth endogenously. The sluggish pace of economic activity abroad and the possible fluctuation of economic expansion still make the U.S. economic growth risky. It is expected that the U.S. economy will grow at the same pace of 2014 this year.