The continuous phase modulation (CPM) signaling scheme has gained interest recently because of its attractive spectral properties. Since the CPM scheme has the phase trellis structure, the maximum likelihood detection at the receiver is employed usually. Thus, the CPM scheme has an attractive error performance, however, the receiver structure is complex. In this paper we propose a variable mapping method which the output data symbols are decided by both the input data bits and the accumulated phase states in order to simplify the detection like PSK. Here we consider the variable mapping method for the two types 1REC and 1RC schemes and evaluate two schemes using this method in terms of both the simplification of detection and error performance.