A new model is presented to predict the radiation response for complementary metal oxide semiconductor（CMOS）devices at low dose rate in space environment. In comparison with the linear system response theory model, the prediction results for CMOS devices at low dose rate radiation by using the new model are more close to actually experiment data, and the experimental results for different dose rate of radiation verify the accuracy of the model. Finally, the radiation effects on sensitive parameters of CMOS devices at low dose rate in space environment are predicted by making use of the new model.