Abstract: During horizon well geosteering, the adjacent well logging data are often used to build the geosteering model in order to guide well drilling. With this model, the depth of target zones can be predicated in the landing process of horizon well. However, the inaccuracy is large if only the adjacent well data is used to forecast the reservoir physical property by interpolation method during horizon well geosteering. Therefore, the seismic inversing method based on model is introduced into geosteering model to predict the reservoir lateral anisotropy. By this method, the drawback of lateral reservoir anisotropy forecast with geosteering model can be over-come, and the well path can be controlled in the reservoirs with good physical properties. Therefore, the reservoir encountering ratio can be increased greatly. It has been confirmed that this method is effective through application to horizon well drilling.