Pointing accuracy is an important index to measure the performance of a telescope system. With the increasing of the aperture， structure size and weight of the telescope， it is more and more difficult to maintain and improve the pointing accuracy. Therefore， it is necessary to make a theoretical analysis of the factors affecting the errors of large telescopes， establish a mathematical model， and correct the pointing errors. In this paper， based on the structural characteristics of large aperture telescope， various factors affecting the pointing accuracy of the telescope were analyzed， and a method of setting up a pointing model to correct the pointing accuracy of the telescope was proposed. The modified model proposed in this paper had clear physical meaning and little correlation of parameters. The model proposed in this paper was used to correct the pointing accuracy of a large telescope， and the root-mean-square error of the azimuth pointing accuracy was 20.6 " before correction and 4.1" after correction， and the root-mean-square error of the elevation pointing accuracy was 5.1 " before correction and 2.8" after correction. Experimental results show that by using the model proposed in this paper， It can effectively correct the systematic errors of the telescope and improve the pointing accuracy.