Thixomolding (R) is a new process of net shape parts for magnesium alloys in one step, and it is suited to manufacture the thin wall products, especially to the electronic component shells. In this paper, the sample of mobile phone housing is fabricated by 220Tons Thixomolding (R) machine made by Japan Steel Works. The effects of barrel temperature, screw rotate rate and mold temperature on microstructure were studied. The relationship between pro cess parameters and microstructure was also discussed in this paper.