The adjustment and application of RTCP function based on system variables of Siemens 840Dsl was introduced. The basic function,prog_event,was used to call the subprogram.CYCLE800 was used to tackle with the swivel data. The related subprogram was programmed to assign the machine tool structure data to the system variables to realize five-axis transformation.Dialogue and ball tool were used to test the accuracy of S shape test piece. The machining requirement is satisfied.