For the characteristic of high pointing accuracy of QiTai 110 m diameter radio telescope, a pointing model is deduced on the relationship between the pointing error and track flatness. Based on the power spectrum function and Fourier series coefficients merging method, a mathematical model of antenna track roughness is established. Through the experiment on a foreign 50 m antenna with completely welded track, antenna elevation angle error is decreased by 1.5″，which provides strong support to achieve high pointing accuracy of antenna research.