Abstract: The effect of grain size on the work hardening behavior of micro SiC_p/Mg during tensile deformation was studied.The results indicate that, after extrusion deformation, SiC_p/Mg materials are extruded with 0.1 mm/s at 170 ℃, 200 ℃and 230 ℃, respectively.The average dynamic recrystallization grains size is 3.9 μm, 7.3 μm and 9.5 μm for SiC_p/Mg extruded at 170 ℃, 200 ℃and 230 ℃.It can be found that the work hardening effect of SiC_p/Mg increases with the improvement of grain size, which is mainly due to the longer absorption time of the grain boundary pair dislocation when the grain size is increasing, resulting in the higher median dislocation density in the material.