Abstract: Evaluating the shape and size of the fracture process zone near mode II and mode III dynamic crack tip is still a problem unsolved at present. An approximate method for evaluating the shape and size of FPZ is proposed and the feasibility of the method is demonstrated through a comparison with the results calculated based on the known stress fields. The shape and size of the FPZ near the dynamic crack tip are determined based on the new method, which depend on the crack propagation velocity. The results show that the FPZ at mode II and mode III dynamic crack tip distributes symmetrically with respect to the crack plane and increases with the crack propagation velocity. FPZ changes more rapidly when the Rayleigh wave velocity is approached. The size of FPZ calculated by Tresca criterion is larger than that calculated by Von Mises criterion.