The invention provides a wastewater treatment device. The device comprises a solid-liquid separation unit, a sodium ion exchanger, a weak acid cationic exchanger, an ultrafiltration unit and a reverseosmosis unit, wherein the solid-liquid separation unit is provided with a wastewater inlet and a liquid phase outlet and used for performing solid-liquid separation on wastewater; the sodium ion exchanger is provided with a first water inlet and a first water outlet, and the first water inlet is communicated with the liquid phase outlet; the weak acid cationic exchanger is provided with a secondwater inlet and a second water outlet, and the second water inlet is communicated with the first water outlet; the ultrafiltration unit is provided with a third water inlet and a third water outlet, and the third water inlet is communicated with the second water outlet; the reverse osmosis unit is provided with a fourth water inlet and a purified water outlet, and the fourth water inlet is communicated with the third water outlet. With the adoption of the device, the effluent conductivity is smaller than or equal to 50 us/cm, the salt removal rate is larger than or equal to 98%, the water recovery rate is larger than or equal to 94%, and zero emission of a thermal power plant is basically realized.