Using high temperature-high pressure maintenance vessels and compression testing equipment etc., stress-strain curves of oilwell cement systems were tested. Influent law of temperature and additives on the compressive strength and elasticity modulus of oilwell cement stone were analyzed. The problem for establishing relationship model between strength and elasticity modulus were researched. The following conclusions are obtained: There are sensible elastic deformation and brittle failure feature in the oilwell cement under monopodium stress conditions. At the beginning, the compressive strength and elasticity modulus of cement stones increase with the increase of temperature. After the temperature after rises a certain value, the compressive strength and elasticity modulus reduce when the temperature continue to be increased. Compressive strength and elasticity modulus of every slurries increase with the increase of curing time. Dispersing agent, filtrate reducer and latex can decline compressive strength and elasticity modulus of the cement stone, but high early agent , expanding agent can upgrade them. Silica sand can also upgrade them at high temperatures. The relationship model between strength and elasticity modulus can be established by using adopting data regression analysis method. Using tested compressive strength, the model established in this paper can be used to estimate cement elasticity modulus of cement stone.