According to the wellhead device for overhauling the check valve without stopping water injection, water injection does not need to be stopped when the check valve at the wellhead of the wellhead device is overhauled, and meanwhile the technological requirements of well backwashing and forward well washing can be met. The device comprises a large four-way joint, a main valve and a test valve, a filter screen pipe, a valve body and a valve deck are further arranged in a valve body of the water injection check valve, an upper screwed plug and a lower screwed plug are installed at the two ends ofthe valve body, and a valve ball, a valve seat and the filter screen pipe are installed on the lower portion of the valve body and in a center hole of the valve body between the valve deck and the baffle. An inlet of the valve body is connected in a pipeline above the up-flow valve in the water injection main line, and an outlet of the valve body is connected with the three-way pipe. The problemsthat a polished oil pipe water injection well can only conduct inverse well washing but cannot conduct forward well washing, waste liquid returned by well washing cannot be measured, and well washingdata cannot be obtained completely are solved. The water injection check valve can be maintained and replaced without stopping water injection, time and labor are saved, it is guaranteed that the bottom hole pressure is not reduced, and the number of lying wells caused by water injection stopping of a water injection well is reduced.