The invention relates to a construction method of grid plates of a louvered water stop trash rack of a pump station. The grid plates and grid plate shafts are included. Each grid plate is in an arc long strip shape, the grid plate shafts are arranged on the upper portions of the grid plates, the two ends of each grid plate shaft protrude out of the corresponding grid plate by certain length and are provided with bearings, and a gear is arranged on the outer side of the bearing at any end of each grid plate shaft. The multiple grid plates are arranged on a left pier wall and a right pier wall in the shaft axial direction. The grid plates are connected with a grid plate opening and closing mechanism on the pier walls. The grid plate opening and closing mechanism is rotated clockwise, the grid plates are rotated upwards to be opened for water passing, and the multiple grid plates form the trash rack to prevent sundries from passing; and the grid plate opening and closing mechanism is rotated anticlockwise, the grid plates are rotated downwards to be closed, and a gate is formed to prevent water flow from passing. Through the adoption of the construction method, land can be saved, thebuilding cost of projects can be saved, sundries can be prevented from entering during water drawing, and the trash rack can be used as the gate for stopping water during maintenance.