Continuous Phase Modulation(CPM) is widely used in wireless communications especially in military communications due to its high power and bandwidth efficiency. A low-complexity sequence detection receiver for CPM was designed in this study. The number of matched filters in the receiver front was reduced by orthogonalizing process. The states of Viterbi decoding were reduced through the state combination. The signal was detected combined with the decision feedback. Analysis and simulation results showed that the algorithm efficiently reduced the computation complexity at a very little sacrifice of performance compared with the optimum Maximum Likelihood Sequence Detection(MLSD).