Abstract: In order to lower the complexity of M-ary Position Phase Shift Keying (MPPSK) signal detection based on support vector machines (SVM), a new method named similar dichotomy SVM with low complexity was proposed after the discussion of common methods for the multiclass classification of SVM. Then a new approach of choosing SVM characteristic vector, known as modulation array method, was proposed, which meant to improve the detection performance of high-order MPPSK system. At last, these two methods were combined to be used in the detection of higher-order MPPSK system. The simulation results indicate that: the complexity of multiclass classification SVM can be significantly lowered and the detection performance of the high-order MPPSK system is effectively improved by using similar dichotomy and modulation array method respectively. And combining these two methods, the complexity can be effectively lowered while the expected detection performance is guaranteed.