To improve the accuracy of long-term storage performance evaluation for solid rocket motor grains and solve the critical limitation of existing models being difficult to simultaneously couple the effects of temperature and aging time， this investigation aims to achieve high-precision prediction of relaxation modulus over a wide range of temperature and the full aging cycle. Based on the stress relaxation data obtained from accelerated aging tests of Composite Modified Double-Base（CMDB） propellant at 343.15 K， a temperature-dependent relaxation modulus model that accounts for aging effects was developed by applying the time-temperature equivalence principle and introducing aging time as an internal variable. The results show that the predicted curves are in good agreement with the experimental data under test temperatures ranging from 233.15 K to 323.15 K and after accelerated aging at 343.15 K for 0-100 days. Thus， it indicates that the developed model can effectively describe the variation of the relaxation modulus for CMDB propellant over a wide range of temperature and the full aging cycle.