Redundant gears should be eliminated in the design of automatic transmissions in order to reduce inertial power loss and manufacturing costs. The purpose of this paper is to present a computerized method for the identification of redundant gears in planetary gear trains. First, the graph representation of planetary gear trains proposed by Hsu and Lam [1–3] is applied to clarify the kinematic structure. Next, based on the concept of fundamental circuits, the criterion for identifying the existence of redundant gears in a planetary gear train is deduced. Using the notation of adjacency matrix, a computer program has been developed for the automatic analysis of the existence of redundant gears in planetary gear trains. The result of this study is of benefit to the design of automatic transmissions for the automobile.