A novel equivalent error calculation and compensation method of inertial sensors is proposed to solve the problem that the navigation error diverges with time in rotating inertial navigation system (RINS). Based on the error model of RINS and the equivalent error characteristics of RINS, DC component are analyzed, earth oscillation term and time divergence term of the navigation longitude and latitude error are analyzed. The main equivalent inertial sensor errors are calculated. With the compensation of the equivalent inertial sensor error, the longitude error is suppressed and the longitude error is reduced from [0.4] to [0.15]. Furthermore, the navigation accuracy is increased by 62.5%. These experimental results illustrate that the divergence of the longitude error can be suppressed, and the DC component and the earth oscillation amplitude of latitude error are reduced by utilizing this novel method, which realize the improvement of the navigation accuracy.