The U.S. economy expanded at a low pace and ended its four quarter-long recession in the third quarter of 2009. After rising at an annual rate of 5 percent，the third highest record in the past 10 years，in the last quarter of 2009，the real GDP growth was continuously slowed down in the first half of 2010 and presented an unstable recovery. Domestic private consumption and fixed investment played key roles in the growth. However，commercial and industry loans is still decreasing，real economic activity does not resume to the pre-crisis level. The high unemployment rate and the low level of core CPI index and capacity utilization indicate the fragility of the recovery. Furthermore，the record-high federal government debt will make it difficult to balance the internal and external economies.Our assessment is that the stimulus package will continue in the near future and the US economy will grow at 2.9% in 2010，and will be around at 2.5% in 2011，if no more shock present.