Abstract: Photorespiration is an important metabolic process in C3 plant，which is one of the highlight of research on photosynthesis. In the article，we elucidate the photorespiratory normal metabolic pathways and alternative pathway of glyoxylate metabolism and function of alternative pathway. The biological characters of key enzymes are discussed. The biologic functions of photorespiration in alleviating stress damage，slowing the degradation of chlorophyll，driving the Calvin Cycle，participating in TCA、nitrogen metabolism、protein accumulation and state transition are summarized.