Abstract: To analyze the shear failure mechanism of precast steel reinforced concrete beams and put forward the corresponding calculation method, two full-scale precast steel reinforced concrete beams were tested under static four-point loading. The failure patterns, load-displacement curves and strain development were recorded to investigate the shear mechanism and strength of the specimens of different aspect ratios. On the basis of the test results, a set of calculation formulas based on the compatible truss-arch model and Nakamura model were proposed to predict the shear strength of both precast and conventional steel reinforced concrete beams. The comparison with the existing results of 75 shear-critical steel reinforced concrete beams shows that the proposed method can provide reasonable predictions of the shear strength, and the results calculated by the AISC 360-2010 model and JGJ 138-2016 model are relatively conservative.