Based on the instrumentation box drawing technology demand, the structure, working principle and  key parts functions of floating trimming die were analyzed. The design of floating female dies motion was introduced in detail. According to the motions, the travel relationship between the punch side and the floating female was studied. Then the dies key part (the guideway) that controled the motion of floating female die was designed. Using the principle of slanting wedge, the vertical direction relative movement of floating female die was changed to the all-around horizontal direction trimming movement. So the dies structure is simplified, and the quality of the drawing piece is guaranteed.