The orientation errors of an alt-alt photoelectric telescope are analyzed to determine the effects of the main errors of telescope on measuring accuracy and to improve the pointing precision.By analyzing optical, mechanical and electrical errors from a measured target to the telescope picture, the measuring equations of alt-alt telescope are established. Then,by using Monte Carlo method, the orientation errors are forecasted and the sensitivity of errors to pointings is analyzed.Furthermore,an error correction model is built based on the high sensitivity errors. The result of correction test indicates that the standard error of the longitude axis rotation angle has reduced by 95% from 66.4″ to 3.3″, and that of the latitude axis rotation angle has reduced by 89% from 49.4″to 5.6″. These results show that the model and the method not only can analyze and synthesize the main errors, but also can provide a reference for the whole design.