The effects of different extrusion temperatures (160, 220 and 230 ℃) on the microstructure and mechanical properties of Mg-7Sn alloy with heterogeneous grain structure were investigated using optical microscope, X-ray diffractometer, electron backscatter diffractometer, transmission electron microscope, and a universal experimental tensile machine. All three extruded alloys contain fine dynamic recrystallized grains and coarse hot-worked grains. The difference in deformability between coarse and fine grains leads to the formation of hetero-deformation induced stress (HDI). The extruded alloys form a typical basal texture, and the texture strength of the basal texture is weakened with increasing extrusion temperature, which is mainly attributed to the fact that the increase in extrusion temperature promotes the dynamic recrystallization and the activation of non-basal slip. The extruded 9E160 alloy exhibits high tensile strength at room temperature (σ_b=341.83 MPa) due to HDI strengthening, fine grain strengthening and high volume fraction of nanoscale Mg₂Sn phase precipitation strength. The increase in extrusion temperature facilitates dynamic recrystallization, resulting in grain refinement and further enhancement of the alloy's plasticity. The improved plasticity of the alloy can be attributed to both grain refinement and activation of non-basal slip systems.