Magnesium alloys are promising for use in many structures due to their low density, high specific strength, and specific stiffness. This study analyzes the microstructure of magnesium alloy materials and uses X-ray inspection to explore the characteristic situations of sparse and segregation defects in magnesium alloys. Combining the finite element method, Taylor strain gradient plasticity theory, the Eshelby equivalent inclusion model, and other fine mechanical simulation methods, finite element simulation and experimental analysis of magnesium alloys containing loose and segregation defects are carried out to systematically analyze the influence of defects on the macroscopic mechanical properties of magnesium alloys. The results show that a small number of defects in magnesium alloy materials have little effect on their mechanical properties, both at room temperature and high temperature. The tensile strength, yield strength, modulus of elasticity, and elongation decreased significantly with the increase in the grade of sparsity and segregation defects. It’s worth noting that the elongation of segregation grade 1 specimens increases slightly, with an increase of 0.64% and 0.35% at room temperature and high temperature, respectively. There is a certain negative relationship between the defect grade of magnesium alloy materials and their macroscopic mechanical properties.