Abstract: Physiology of EPSP synthase was briefly reviewed.The enzyme is a chloroplast localized enzyme of the shikimate pathway in plants.Cytosolic precursor,the pre EPSP synthase,becomes mature EPSP synthase after a cut process of the amino terminal transit peptide of cytosolic precursor in the chloroplast.There are three activity domains in 3D structure of EPSP synthase,and single amino acid replacement in the three domains could confer glyphosate tolerance.It was identified there are glyphosate binding sites in the three domains.EPSP sythases in various species are significantly similar.Mechanism of the reaction catalyzed by EPSP synthase is as follows:enzyme bound PEP becomes intermediate enzyme PEP,then combines with S3P to form enzyme bound ketal,then produce EPSP.Glyphosate,as a transition state inhibitor of EPSP synthase,inhibit the canalization of the enzyme as an EPSP synthase·EPSP·glyphosate ternary complex.Intermediate mimic inhibitors from EPSP derivative and S3P·glyphosate can inhibit EPSP synthase activity.