The invention provides a water injection well segmental water injection device, which comprises a plurality of packers, a plurality of water distributors and a control device, wherein the plurality of packers are arranged at intervals in the length direction of a water injection well so that the water injection well is separated into a plurality of well segments; the plurality of water distributors are arranged in the plurality of well segments in a one-to-one correspondence way; and the control device is electrically connected with the plurality of water distributors so as to control the opening size of a water outlet of each water distributor. The water injection well segmental water injection device provided by the invention has the advantages that the quantity of water entering each well segment can be effectively controlled; the structure is simple; the realization is convenient; and the cost of the segmental water injection process of the water injection well is effectively reduced.