Hole azimuth angle correction is very important in directional well trajectory control and target-hitting analysis. By the analysis on the relationship between geodetic coordinate and Gauss-Kruger projection coordinate; and based on the geomagnetic field spherical harmonics model, geomagnetic parameters and meridian convergence angle calculation model, the realizing way and the solving steps are put forward and corresponding calculation software are programmed. With the practical calculation and analysis, the importance of accurate calculation of geomagnetic parameters and meridian convergence angle in directional well trajectory control is shown.