The　response　of　the　long-span　cable-stayed　bridges　under　seismic　load　is　complex.　Reasonable　methods　is　very　important　to　analyze　the　seismic　performance.　In　this　paper,　a　practical　project　is　taken　as　research　background　which　is　double　pylon　cable-stayed　bridge　with　main　span　of　416m.　Two　artificial　seismic　waves　and　two　seismic　records　were　selected　to　analyze　the　seismic　behaviors　by　the　response　spectrum　method,　time　history　analysis　method　and　power　spectrum　method.　The　result　shows　that　seismic　responses　of　the　girder　and　main　tower　are　basically　identical　under　the　effect　of　artificial　seismic　wave.　The　response　spectrum　analysis　results　of　them　are　between　the　other　two　methods　under　the　effect　of　the　natural　seismic　wave.　For　stay　cable,　time　history　analysis　results　has　great　difference　compared　with　results　of　other　two　methods.　Therefore,　different　methods　should　be　choosed　base　on　specific　circumstances　to　analyse　the　earthquake　response　of　this　structure.