The accelerated high-temperature test was carried out to understand the influence of rehydration of unhydrated cement under different curing temperature and W/B on the performance of ultra high performance concrete(UHPC) with the test of loss on ignition method,mechanic performance, deformation test, RCM and carbonation test. The results show that the rehydration of unhydrated cement in UHPC could be accelerated effectively when the curing temperature was 60 ℃.The bound water content was stable in 90 d. With the increase of age, UHPC would first shrink and then expanse. It would have a downside on the development of its performance in 90 d, such as flexural strength, resistance to chloride ion permeability and carbonation resistance. There was no obvious change of compressive strength. Moreover, the lower W/B, the higher increased percentage of bound water content of UHPC in 90 d, the greater expansion value, and the higher the flexural strength loss rate.