A　semi-analytical　model　of　the　aerodynamic　damping　for　horizontal　axis　wind　turbines　was　established.　Considering　the　translational　and　rotational　degrees　of　freedom　of　tower-top,　aerodynamic　damping　forces　on　the　rotor　were　calculated　by　the　blade　element　momentum　theory　and　simplified　to　a　resultant　force　at　the　tower-top　and　a　resultant　couple.　Thereafter,　the　semi-analytical　solution　of　modal　aerodynamic　damping　ratios　was　suggested.　Subsequently,　the　modal　aerodynamic　damping　ratios　of　the　NREL　5　MW　and　WP　1.5　MW　wind　turbines　were　calculated　by　the　semi-analytical　solution　and　identified　from　their　dynamic　response　to　validate　this　solution.　And,　the　sensitivity　analysis　was　performed　to　evaluate　the　influence　of　control　parameters　on　the　modal　aerodynamic　damping　ratios　of　wind　turbines.　Finally,　the　uncouple　analysis　method　with　this　aerodynamic　damping　model　was　used　to　predict　the　dynamic　response　amplitude　of　wind　turbines,　wherein　the　aero-servo-elastic　fully　coupled　analysis　were　set　as　the　reference　method　to　examine　the　reliability　of　this　uncoupled　method.　The　results　indicated　that　the　uncoupled　analysis　method　employing　this　aerodynamic　damping　model　can　accurately　predict　the　dynamic　response　of　horizontal　axis　wind　turbines　excited　by　a　combined　wind-earthquake　loading,　which　is　significantly　better　than　the　existing　uncoupled　model.