GMSK is the main digital frequency modulation mode used by airborne sonar buoy at present.To solve the problems of low accuracy and waste of resources when Look-Up Table (LUT) technology is used to replace the complex filtering,integration and sine cosine function solution in GMSK digital modulator,based on the research and analysis of GMSK modulation signal,the mathematical model of Gaussian pre-modulation signal is improved,the mapping relationship between the associated symbol and GMSK signals at all levels is derived,and the optimized and simplified LUT is selected to design the GMSK orthogonal modulation scheme,which not only ensures the algorithm accuracy,but also minimizes resource utilization.