The invention discloses a filter unit for a kitchen sink. The filter unit comprises a main board and an auxiliary board, wherein second supporting plates are fixedly connected to the surface of the main board, and a plurality of first supporting plates are fixedly connected between the second supporting plates; water outlets are formed among the first supporting plates; grooves are symmetrically formed in the surfaces of the second supporting plates; a snap joint is arranged on the back of the main board, and is combined with a clamp slot in the surface of the auxiliary board in a clamped manner; the surfaces of the auxiliary board and the main board are symmetrically fixedly connected with the second supporting plates and the first supporting plates; the second supporting plates on the surface of the main board are in crossed clamping with the second supporting plates on the surface of the auxiliary board. According to the filter unit, a human hand is prevented from extending to the bottom of a sink during draining, so that hands of users can be protected, and the influence that a plug cannot be opened conveniently because of over high hydraulic pressure can be avoided.