Abstract: The Iosipescu shear test has been investigated by a number of researchers and conflicting results have been reported. In this paper, a combined experimental and numerical approach is adopted to investigate the mode-Ⅱfailure mechanism of concrete subjected to four-point-shear loading. The process of the crack propagation and the angle θc of the crack initiating propagation are analyzed. The finite element method is used to study the stress distribution around the crack tip. The effect of the distance from the loading location to the crack surface on mode-Ⅱfailure mechanism of concrete specimen is studied. It is concluded that decreasing the distance from the loading location to the crack surface will lead to the increase of K_Ⅱc. Besides, the crack which initiate propagating from the notches, is not in the direction of the dominate shear stress. Thus, the failure is essentially not due to shear fracture.