The invention provides an upper end cover of a filter element. The upper end cover comprises an end cover main body, wherein a positioning structure which is used for positioning the filter element is arranged on one surface of the end cover main body, a water fence is fixedly arranged on the other surface of the end cover main body and surrounds the end cover main body, and an accommodating space is formed by the water fence and the surface of the end cover main body. The invention further provides a filter element assembly and a water purifier. By arranging the water fence on the upper end cover of the filter element, fed water is intercepted by the water fence firstly, uniformly escapes from the upper edge of the periphery of the water fence and then flows downwards to enter the filter element such as PP (polypropylene) for filtration, so that the water fed into the filter element from the outside can be uniformly distributed, and the filter element can be fully used.