Abstract: In order to meet the requirements of heavy oil thermal recovery on cementing cement, this simulation of heavy oil thermal recovery well cement at room temperature solidification, high-temperature thermal recovery of the formation of this special environment, first slurry at atmospheric pressure at 70 ℃ for three days later by a thermal temperature and pressure conservation. In this paper studies at different high temperatures silica sand grain size on the impact of cement strength development as well as the different Ca/Si ratio on impact of the recession of well cement at different high temperature gradient, described the reason that the silica sand grain size and Ca/Si ratio can improve the strength and thermal stability of cement, found the best silica sand grain size and Ca/Si ratio from the mechanism. The studies have an important guiding significance in heavy oil recovery and develop. What is more, it provides a basis for further selection and design of heavy oil slurry system.