The system errors of the rotary steering drilling tool are included in the designed points of the correction matrix. The correction matrix error occurs, which is one cause of low precision attitude angle under near-vertical position compensated by the traditional correction (TC) . Average balance correction (ABC) can compensate for the correction matrix error, but the posture error in the whole self-rotation cycle is still uneven. A kind of equiangular interval balance correction (EABC) model is formulated based on the equal angle interval, the expressions of correction matrix error are induced, those influence characteristics on the posture accuracy are investigated, and the experimental data are computed respectively with TC, ABC, and EABC. The computed results show that compensated by EABC, the average inclination angle errors are lower than 0. 012°, and the peak-to-peak inclination angle errors are lower than 0. 027°. The average tool face angle errors are lower than 0. 008°, the peak-to-peak tool faces angle errors are reduced to 54 ~ 95 percent of those by ABC, and the standard deviations of tool face angle error are decreased to 40 ~ 63 percent of those by ABC, which means that EABC further reduces the absolute error under near-vertical positions, then improves the attitude angle accuracy.