Aiming at the problem that projectile body geomagnetic survey is susceptible to various errors, which leads to the decreasing of the geomagnetic attitude measurement accuracy, the geomagnetic measurement error of the ellipsoid model is established on the basis of analyzing its own errors and environment errors, the maximum likelihood estimation algorithm is used to solve the static error compensation coefficient; taking the static error coefficient as initial value, recursive least squares method is adopted to obtain the real time update algorithm of the error coefficient. From above studies, the online combination correction algorithm for geomagnetic measurement error compensation is formed. The simulation and experimental results show that the maximum attitude angle error is less than 5° in near blind zone direction, the online combination correction algorithm can ensure the accuracy of the attitude detection system under different shooting conditions.