<p>The solid propellant is a particle-reinforced material with significant tension-compression asymmetry. Based on the constant-speed tensile test, constant-speed compression test, and cross-sectional SEM scanning test, this study investigated the differences in the mechanical properties of the HTPB propellant under tensile and compressive loading and the underlying mechanisms. The results show that the tensile strength of HTPB propellant is much smaller than compressive strength. According to the SEM test results of the failure surface, the tensile mechanical properties of the propellant are mainly affected by matrix, and the influence of particles on the mechanical properties is more obvious during the compression process. According to test data, a tension-compression integrated nonlinear constitutive model was constructed, and its application in simulation calculation was realized. The results show that the theoretical, simulation calculation and test results are in good agreement. At 15% strain, the maximum error between the theoretical results and the experimental curve is 9.1% and 4.8% respectively in the process of tension and compression. Therefore, the model can accurately describe the stress-strain relationship of HTPB propellant under different strain rates of tensile and compression. This model can provide theoretical support for accurately evaluating the structural integrity of SRMs.</p> Graphical Abstract <p></p>