Abstract: In order to study the effects of the semi-solid molding technology on its microstructure, mechanical properties and corrosion behavior of AZ91D magnesium alloy, through the heat treatment and electrochemical corrosion analysis of the semi-solid injection-formed magnesium alloy, the microstructure and properties changes of the magnesium alloy forming parts after injection and heat treatment were studied. The results show that compared with the die-cast magnesium alloy, the semi-solid injection magnesium alloy has uniform microstructure, excellent mechanical properties, fine grains and average grain size of 20-30 μm, which can obtain good quality microtissue. The heat treatment of magnesium alloy has a great influence on the number and distribution of the second phase at the grain boundary and can act on the material properties.After aging treatment, the hardness of magnesium alloy increases from 63.47 HV to 74.05 HV, and the tensile strength increases from 125.56 MPa to 150.91 MPa, the tensile strength is increased by 20.2%. In the electrochemical corrosion of NaCl solution with a mass fraction of 3.5%, the self-corrosion potential of the alloy is-959.56 m V. After solid solution+aging treatment, the self-corrosion potential first increases to-927.55 m V and then decreases to-988.94 m V, and the corrosion resistance increases first and then decreases.