The utility model discloses an assembly type precast concrete stress testing device, which relates to the technical field of concrete stress detection and comprises a bottom plate, T-shaped sliding grooves are formed in the left side and the right side of the upper surface of the bottom plate, and T-shaped sliding blocks are connected in the two T-shaped sliding grooves in a sliding manner. The utility model discloses an assembly type precast concrete stress testing device. A T-shaped sliding groove, a T-shaped sliding block, a supporting plate, a second sliding sleeve, a second sliding rod, aclamping groove, a pull ring and a second spring are arranged; when people control the extrusion plate to fix concrete through the electric push rod; the pull ring drives the second sliding rod to move upwards; and then the U-shaped plate is manually pushed to move forwards or backwards in the T-shaped sliding groove, the pulled pull ring is loosened, and the second spring drives the second sliding rod to be clamped into the clamping groove through the pull ring, so that the U-shaped plate can be stably fixed, people can conveniently adjust the position of concrete, and convenience is broughtto workers to detect the concrete.