Considering the huge and transient force in the spool opening process of the hydraulic press, a cam profile curve design method based on the combination of two arcs was presented. The method aims at getting small pressure angles when the driving force reaches its maximum value and getting a fast opening speed in the whole process by finding a suitable combined two-arc curves. The mathematical model of the cam profile was established on the basis of homogeneous coordinate transformation, whose kinematic characteristic was investigated by using equivalent slider crank representation. This method was applied on the cam design of the spool drive system in 300MN die forging hydraulic press. The cam has good flexibility and small impact. Industrial field application shows that the cam designed in this method can effectively reduce the frequency of equipment failures. This method provides guidance for cam design on the condition of heavy and transient load.