Abstract: The molecular dynamics method was used to study the damage of GaN irradiated by proton in this paper. By studying the cascade collision caused by primary knock-on atom (PKA) with different energy of 1-10 keV, the relationship between the point defect and the PKA energy, the evolution law of point defect with time, the spatial distribution of point defect and the point defect cluster size characteristic were analyzed. The result shows that the production of point defect is linear with the PKA energy, the evolutions of different types of point defects with time are similar, point defects are mostly produced along the PKA trajectory, and most of point defect clusters are isolated point defects and small clusters.