The mechanism of opto-electrical stabilization is widely used in the field of observation and measurement of the armament. Its pointing accuracy relates the realization of function as target realization or tracking. As the important source of pointing error, the geometric error of the mechanism is inevitable. So the paper develops the model of pointing error using the method of multi-body system error's development, which adopts the azimuth-elevation mechanism as the example. The effects of error sources are also compared according to the statistical and sensitivity analysis. The research can be applied not only to the estimation of pointing error during designing, but also to the allocation and calibration of errors.