Apelin is an endogenous ligand of the apelin receptor(APJ),a seven-transmembrane G protein-coupled receptor.Apelin and APJ exist in a variety of tissues,with special status in the heart,lung and tumors.Furthermore,many research shows that the apelin/APJ system exerts a broad range of activities that affect kidney systems.This review we summarize the role of apelin/APJ system on renal fibrosis,renal ischemia/reperfusion injury and diabetic nephropathy,polycystic kidney disease,hemodialysis.It was found that the level expression of apelin m RNA in the inner stripe of kidney outer medulla was the highest,and the region is significantly correlated with water and sodium balance.In UUO mice model,intraperitoneal injection of Apelin can reduceα-SMA,the expression of TGF-1 and its receptor,and between renal stromal components also significantly decreased.These results show that Apelin can reduce the deposition of ECM and improve renal interstitial fibrosis.In renal ischemia/reperfusion injury studies show that apelin-13 can significantly reduce the damage induced by renal tubularlesions,renal cell death and the normal renal function is not completely lead to large damage.But in diabetic nephropathy,Apelin-APJ system can promote or slow DN disease progression is controversial,still needs further research.Analysis the receiver operating characteristic curve found that in the process of identifying ADPKD disease apelin and copeptin shows good receiver operating characteristic curve(ROC),cox proportional hazards regression model also showed apelin can predict on the progress of kidney disease.In hemodialysis patients the apelin levels and PTH levels were positively correlated,it could prompt apelin can protect bone dialysis patients.Apelin also can reduce Pit-1 inhibition of vascular smooth muscle cell osteoblast calcification and thus improve the aortic calcification,so Apelin may have a potential role in the treatment of vascular calcification in CKD.In kidney disease conditions,Apelin/APJ system plays a variety of biological functions,because of the Apelin protective on kidney,Apelin/APJ may be a potential material for the treatment of chronic kidney disease. Apelin is an endogenous ligand of the apelin receptor (APJ), a seven-transmembrane G protein-coupled receptor. Apelin and APJ exist in a variety of tissues, with special status in the heart, lung and tumors. Manyrthermore, many research shows that the apelin / APJ system exerts a broad range of activities that affect kidney systems. This review we summarize the role of apelin / APJ system on renal fibrosis, renal ischemia / reperfusion injury and diabetic nephropathy, polycystic kidney disease, hemodialysis. It was found that the level expression of apelin m RNA in the inner stripe of kidney outer medulla was the highest, and the region is significantly correlated with water and sodium balance. UUO mouse model, intraperitoneal injection of Apelin can reduce alpha- SMA, the expression of TGF- 1 and its receptor, and between renal stromal components also significantly decreased.These results show that Apelin can reduce the deposition of ECM and improve renal interstitial fibrosis. In renal ischemia / reperfusion injury studies show that apelin-13 can significantly reduce the damage induced by renal tubularlesions, renal cell death and the normal renal function is not completely lead to large damage. But in diabetic nephropathy, Apelin-APJ system can promote or slow DN disease progression is controversial , still needs further research. Analysis of the receiver operating characteristic curve found that in the process of identifying ADPKD disease apelin and copeptin shows good receiver operating characteristic curve (ROC), cox proportional hazards regression model also showed apelin can predict on the progress of kidney disease .In hemodialysis patients the apelin levels and PTH levels were positively correlated, it could prompt apelin can protect bone dialysis patients. Apelin also can reduce Pit-1 inhibition of vascular smooth muscle cell osteoblast calcification and thus improve the aortic calcification, so Apelin may have a potential role in the treatment of vascular calcification in CKD. kidney disease condit ions, Apelin / APJ system plays a variety of biological functions, because of the Apelin protective on kidney, Apelin / APJ may be a potential material for the treatment of chronic kidney disease.