A shear wall cast with tenon-and-mortise precast concrete blocks replacing formworks is characterized in that two blocks with vertically and bilaterally corresponding fastened tenon-and-mortise structures are spliced to form a masonry with a structure, internal cavities of the structure are vertically and completely communicated and horizontally locally communicated, the structure is provided with external level crevices and vertical staggered joints, vertical and horizontal reinforcing steel bars are placed in the internal cavities in the masonry respectively, and concrete is cast. When the shear wall is constructed, a '_' wall, a 'T'-shaped wall or an 'L'-shaped wall can be built only by two types of blocks are needed, a formwork system is no longer set up, waiting for maintenance of the concrete is no longer needed, and continuous operation can be performed. When the used blocks are self-locked in a tenon-and-mortise manner in a horizontal layer, and the vertical reinforcing steel bars can be conveniently fastened in the internal cavities of the shear wall by fastening from two sides to the center.