The sheet metal forming of magnesium alloy is studied. A novel hydro-mechanical deep drawing for magnesium alloy sheets at gradient temperature is proposed on the basis of the study in this domain, the properties of magnesium alloy and the forming characteristics of workpiece in deep drawing. It is indicated that the deep drawing operation should be done in the warm condition and the temperature gradient of workpiece is necessary. The essence why the limited drawing ratio can be improved by means of the new process is demonstrated. The proper temperature gradient can be obtained by the control of the hydraulic during deep drawing operation. Thus the feasibility of the new technology is verified. It plays a solid foundation for solving the forming problem of magnesium alloy sheets and designing the novel setup of hydro-mechanical deep drawing with gradient temperature.