Abstract: In this paper, the fundamental principle of dynamicphotoelasticity is introduced. Someissues concerned such as the applicability of stress-opticslaw and whether the inertia force can be neglected or not etc., are answeredtheoretically. Based on summarizing all sorts of identification ways, amethod to combine stress wave theory with analyzing isochromatic fringesis proposed. As a result, not only the concept of identification is made more distinct, but also the accuracy of analysis and identification can beincreased.