The invention provides a post-cast strip blocking brick structure and a construction method thereof. The structure comprises I partition bricks, a water stop steel plate, a supporting rib, upper faceribs and bottom face ribs. Each I partition brick is in an I shape, wherein the bottom face is a plane, the top face is provided with a longitudinal groove and transverse grooves, and the longitudinalgroove communicates with the transverse grooves. The grooves are used for containing the upper and bottom face ribs. The bottom faces of the two I partition bricks are stacked vertically to form a supporting pillar structure, and the water stop steel plate is arranged between the two I partition bricks. The water stop steel plate is perpendicularly connected to the supporting rib which is vertically arranged. The upper face ribs are arranged in the grooves of the upper I partition brick, and the bottom face ribs are arranged in the grooves of the lower I partition brick. The I partition bricks a plate and post-cast strip interface, and the water stop steel plate extends into a post-cast strip from a plate. The structure is firm and high in stability, and construction time can be greatly shortened. The invention further provides a construction method of the above post-cast strip blocking brick structure, and the construction quality and the construction efficiency are greatly improved.