Field observation is carried out to measure the wave uplift load of cover plate in perforated caisson.The processes of tidal level and uplift load are analyzed by a single day,a short period and the whole period,including the load process and time duration.The statistical result of load process and time duration of elevation up by 0.5 m is compared with the original elevation.It can be found that the rising process of uplift load grows in step with the tidal level.The uplift load is induced together by the tidal level and wave action.The load order for different bins from large to small is the back,middle and front.The uplift load would be obviously improved if the elevation of cover plate is raised by 0.5 m.The elevation plays a decisive role on the state of uplift load for cover plate in perforated caisson.