The high temperature tensile properties under the typical simulated environment of C/SiC composites prepared via polymer infiltration and pyrolysis （PIP） method were investigated.The high temperature tensile property data of the C/SiC composites under different variable conditions （about 3 000 s） were obtained.The high temperature bearing behavior and its variation law of the C/SiC composites under different variable conditions were discussed. The results show that the tensile strength of C/SiC composite material can still maintain about 60% after about 3 000 s complex step heating. The high temperature tensile property retention of C/SiC composite material increases after thermal shocks with large temperature difference. The highest temperature tensile property retention exceeds 80%. The larger thermal shock temperature variation and longer holding time after thermal shock， which is more beneficial to maintian and improve the high temperature tensile properties of C/SiC composites.