The new technique to improve forming property of sheet metal was put forward, stress on thickness of sheet metal has been decreased with drawing-hole drilled on round angle of die, and optimization of the sheet metal forming property was then achieved. Taking cylinder cup with flange as study example, deep drawing cylinder cup with flange was simulated by finite element method (FEM). It was verified theoretically with thickness reduction on critical section and FLD chart of cylinder cup with flange after deep drawing, the forming property and mechanism of new process was analyzed, and the technical key to improve forming property of sheet metal was proposed.