A new method based on modulation domain enhanced subcarrier stripping is proposed to solve the problem ofGPS M code authorization stream acquisition. The proposed method utilizes the start chip correlation between the GPS C/Acode and M code, and uses BOC modulation short code information to accumulate and enhance the GPS M code signal in themodulation domain to obtain the authorized code stream. First, the disclosed GPS C/A code is used to assist in obtaining thecarrier phase and C/A code phase of the GPS signal. Then, the GPS signal carrier phase and the C/A code phase are used toseparate the GPS C/A code from the intermodulation and complete the initial phase alignment of the M code authorizationcode, respectively. Furthermore, the BOC modulation short code information is used to realize the accumulation enhance.ment in the modulation domain, complete the subcarrier stripping, and obtain the GPS M code authorization code stream. Fi.nally, the effectiveness of the proposed method is verified by the actual collected signals, and compared with the existingmethods. The results show that the proposed method can overcome the influence of P(Y) signal sidelobe energy on M codeauthorization code extraction in the bandwidth, and bring a performance improvement of about 3.5 dB.