Optical Solar Reflectors (OSR),also called as rigid secondary surface mirrors,is used as passive thermal control coating in spacecraft,assisting in maintaining the designed operating temperature.OSR play a critical role in the thermal management of space assets through reflection of incident solar energy and emittance of infrared heat.In space irradiation environment,solar absorptance and emittance of thermal control coating will decay.This paper study the space environment stability of improved optical solar reflector(OSR).Simulative examination corresponding to 15 years space environment has been performed.Five types of OSRs have been studied:fused quartz substrate silver OSR、CeO2-doped glass substrate silver OSR、fused quartz substrate aluminium OSR、CeO2-doped glass substrate aluminium OSR and non conductived fused quartz substrate silver OSR.After the ultraviolet,electron and proton simulated irradiation,and atomic oxygen test,the decay data of thermal control performance have been given.Thermal performance and space stability reliability are analyzed.The absorptance degradation of OSR are less than 0.02 after ultraviolet irradiation,less than 0.012 after electron and proton simulated irradiation,lessthan 0.005 after atomic oxygen test.These results are showed that the long stability of thermal control performances of OSRs in space irradiation environment can satisfy satellite design demand.The study results for 15 years environmental effects on degradation of OSRs can supply reliable bases for thermal control design and material selection.