Abstract: Based on the theory of ocean loading tide,by using NAO99b global ocean tide model,the ocean tidal displacement corrections for some IGS stations in China are calculated.These corrections are also applied to GPS data processing.The GPS baseline components and station coordinates computed by the GAMIT software with and without these corrections are computed,compared and analyzed.The results show that the ocean tidal displacement corrections have effects both on GPS baseline components and on station coordinates.To short time GPS data processing,the corrections are more than 1mm;but to long time processing,the corrections have little effects.