Based on the orthogonal 1-shift correlation envelope detection technique, this paper proposes the orthogonal 0/π modulation scheme and improve the precision of the tracking system aimed at the monopulse single channel tracking system. The angle error percentage are less than 1/10 when SNR is 8 dB and the sum-differential channel phase difference changes in the range of -20 to 20. The angle error percentage are less than 3‰ when the sum-differential channel phase difference is 0 and SNR changes in the range of 0 to 10 dB . Compared with the traditional 0/π modulation scheme and the 4-phase modulation scheme, the angle error percentage of this orthogonal 0/π modulation scheme has improved by 50%.