Abstract: The stator of hydraulic motor is a key component which determines performances and working life of an internally curved hydraulic motor. To finish it's internally curved surface conventionally demands a cam actuated profiling machine. The computation of the cam requires high accuracy and so it has to be computed with an electronical computer. This paper describes the design of stator curve, the computation of the cam and the source program of electronic computer. Finally this paper provides a practical example to describe all the procedures of the cam profile computation.