Abstract: Photorespiration,a tightly correlated process with photosynthesis,is initiated by the oxygenation of ribulose-1,5-bisphosphate (RuBP),a process catalyzed by RuBP carboxylase/oxygenase. In this reaction,2-phosphoglycolate,a compound toxic to photosynthesis is produced and recycled back to phosphoglycerate (3-PGA),a Calvin cycle intermediate. Because of production of CO₂ and NH₃,and the considerable loss of energy,this cycle is considered a wasteful process. However,under high light intensities,photorespiration could also alleviate photo-inhibition and photo-oxydation by adjustment of electron flow and consumption of excess energy. The gene cloning of this process could facilitate studies on physiological functions and increase crop yields by modifying key genes. In this article,the process,physiological functions,gene cloning and regulation of this pathway are summarized.