Abstract: To resolve the problem of lineofsight (LOS) drift caused by the earth’s rotation in gyrostabilized platform, a LOS drift compensation method based on inertial attitude parameters was proposed. According to the geographic coordinate and the platform’s attitude information computed by the inertial system, the method calculated the earth rotation angular rate’s projection on the optoelectronic stabilized platform coordinate system. Using this projection, the sightstabilizing control unit compensated the speed feedback signals, thereby the LOS drift caused by earth’s rotation was reduced. Test results show that using the compensation method, the azimuth drift amount is 1.69 mrad/h and the pitch drift amount is 1.84 mrad/h, far less than the drift amount of 6.89 mrad/h in azimuth orientation and 7.32 mrad/h in pitch orientation without using compensation method,which proves that this method can effectively control the LOS drift.