A beating motion is one of the main motions of the rapier loom. The beating motion locates yarn to a desired position after weft insertion motion. There are two kinds of mechanism for beating motion. One is crank lever type and the other is double cam type. Crank lever type usually used low speed rapier loom. In other hand double cam type used high speed rapier loom. Cam part in double cam type beating mechanism is very important. Cam design starts at displacement curve design. This study investigated four different displacement curves selected from various kinds of displacement curve functions. Thus this paper proposed how to select optimized displacement curve function for double cam type beating mechanism of high speed rapier loom using cam simulation. And then, presents the comparable data of pressure angle, cam contact force and driving torque per each of displacement curve to determine the optimized displacement curve function.