In this paper, the resonance signal of the rubidium optical pumping magnetometer was studied. The theory is based on the quantum physics and atomic physics. Through establishing the relation between the magnetic sub-level rate equations and the light intensity, the angular dependence of the resonance signal was discussed. When θ=0° the resonance signal is maximum, when θ=90° the signal strength becomes zero, and the equipment won't work. Through the simulated curves, the relationship between the resonance signal and the relaxation time as well as the density of rubidium vapor has also been done. This research provides a theoretical basis to solve the key technology of posture correction. As the rubidium vapour magnetometer measures the underwater geomagnetic field, it also plays a vital role for improving the accuracy of the instrument.