The objective of the study is to investigate a new method for the preservation of carambola fruits and the effects of exogenous citric acid on ripening,senescence and preservation of post harvested carambola fruits.Carambola fruits were subjected to treatments of citric acid at the concentrations of 0(as control),5mmol/L and 10mmol/L for 20min,and then were stored at 15℃.The physiological parameters related to delaying ripening and softening process were measured.The results showed that citric acid treatments decreased the softening rate,delayed the increase of total soluble solids(TSS) and delayed titratable acid(TA)decreasing.Compared with the control,the membrane permeability was distinctly inhibited,and the loss of VC content was decreased.Citric acid treatment can promote the activities of peroxidase(POD) in later period of storage,and decrease polyphenol oxidase(PPO) activity and malondialdehyde(MDA) content.Correlation analysis showed that the physiological parameters of POD activity,PPO activity and TA content were related to the firmness in carambola fruits.It is suggested that exogenous citric acid treatment could delay the ripening and senescence rate of carambola fruits.