The present invention discloses a desulfurization wastewater lateral flow net curtain type precipitation separation apparatus and a method thereof. The precipitation separation apparatus comprises a homogenizing water distribution zone, a solid liquid separation zone and a water outlet zone, wherein the homogenizing water distribution zone is positioned at the water inlet end of the precipitation separation apparatus, and comprises a perforation water distribution system and a perforation water distribution flower wall, the perforation water distribution system is positioned at the bottom portion of the homogenizing water distribution zone, the perforation water distribution flower wall is arranged at the water outlet end of the homogenizing water distribution zone, the solid liquid separation zone is positioned at the middle section of the precipitation separation apparatus, the bottom portion of the solid liquid separation zone is provided with a sludge hopper, plural groups of fiber net curtains arranged at equal intervals and perpendicular to the water flow direction are arranged in the solid liquid separation zone along the water flow direction, the water outlet zone is positioned at the water outlet end of the precipitation separation apparatus, and a perforation flower wall is arranged between the solid liquid separation zone and the water outlet zone. According to the present invention, the fiber net curtain has the high specific surface area, can effectively adsorb suspended particulate matter and supersaturated salt ions in the wastewater to form the deposition and crystallization center so as to promote the solid-liquid separation, and is targeted and efficient for the desulfurization wastewater of the power plant.