In order to study the difference of organic acids contents and citrate acid metabolism enzyme activities in peach fruit inside and outside the greenhouse,the method of high performance liquid chromatograph(HPLC) was used to analyze the content and composition of organic acids, and the activities of citrate acid metabolism enzymes were measured during the development of Chunmei peach fruit inside and outside the greenhouse.The main results showed that the content of titratable acid first increased and then decreased during the development of Chunmei peach fruit.The titratable acid content in the matured fruits in the greenhouse was 0. 49%, which was significantly higher than that(0.27%) outside the greenhouse.The kinds of organic acids in the Chunmei peach fruit inside and outside the greenhouse were mainly malic acid,citric acid,quinic acid and shikimic acid,of which malic acid had the highest content,and the proportions were 49.62% and 56.47%,respectively.However,the difference in citric acid content between inside and outside the greenhouse was the largest among all kinds of organic acids,and the proportions of citric acid were 25.31% in the greenhouse and 14.86% outside the greenhouse,so it was showed that the higher content of cirtic acid in the matured fruits was the main reason to result in the higher total acid content inside the greenhouse. Relationship between the content of cirtic acid and the activities of its metabolism enzymes indicated that the higher activity of NAD-IDH at the former stage of fruit development in the greenhouse resulted in lower content of cirtic acid,while the higher CS and PEPC activities in the late stage of fruit development inside the greenhouse resulted in higher content of citric acid.