Health care reform has been one of the most important domestic issues in the Obama administration’s agenda. After 15-month-long efforts，President Obama signed and promulgated the Patient Protection and Affordable Care Act （PPACA）on March 23，2010. This paper describes the background and problems of health insurance market in U.S. before the reform，briefs the main contents of PPACA，analysises the possible effects and influences of its implementation. The author believes that the law will be alleviated to some extent the increasing rate of the uninsurance and expanding health insurance coverage. It’s so difficult to achieve the universal insurance because of many obstacles in U.S. health policy-making procedure. The vital acitivities of the health reform in U.S. are thoese innovations on the health care financing system，delivery system and payment system. Those innovations will improve the efficiency and fairness of the health insurance system. However，the lack of comprehensive measures will have impact on the effectiveness of the reform.