Parallel strand bamboo (PSB) is a high-strength bamboo composite that has been used in construction in recent years. Crack growth is a major concern in the design of PSB components for building structures. This study investigated the mode II fracture properties of PSB composite under in-plane shear action, starting from the end notched flexure (ENF) test as the prototype of specimens. The compliance based beam method (CBBM) was used to analyze the crack propagation process. The results showed that crack propagation of mode II fracture of PSB was self-similar cracking with cracks parallel to the strand. The fracture process contained two stages: the development of the Fracture Process Zone (FPZ) and the crack propagation stage. The critical energy release rate GIIc was a constant independent of the initial crack length, with a mean value of 2.61 N/mm; the mean value of fracture toughness KIIc was 4436 kN·m-3/2, which is greater than those of commonly used timber products. The R-curve showed a gradual increase before crack extension due to the development of the FPZ but became approximately horizontal during crack propagation.