The relations between U.S. and China are more fluctuant，competitive，sensitive in 2010，with a widening recognition gap between the official and the public opinion on both sides. This is because the comprehensive transformation of the environment in which the bilateral relations have been unfolded in the Post-Crisis Period. Such environmental transformation not only causes the periodical change of the Obama administration’s China policy which inevitably leads to the fluctuation of the relations，but also makes the deep bilateral problems more apparent，such as the ambiguous nature of the relations and the weakening of relation structure，etc. In order to avoid strategic showdown and deepen strategic cooperation，the two sides are dedicated to the rebalancing efforts during the second half of 2010 even with their competition still going on. Up to now，it seems that the U.S-China relations turn back to stabilization after Chinese President Hu’s visit to Washington in early 2011. But this stabilization is fragile and reversible due to the existence of a serious of old and new problems.