Objective:To observe the serum level of fibroblast growth factor-23(FGF-23) in patients with end stage renal disease (ESRD) and study its association with phosphorus and vitamin D metabolism.Methods: Serum FGF-23 level was determined by enzyme-linked immunosorbent assay (ELISA) in ESRD patients undergoing haemodialysis (HD, n=50) and peritoneal dialysis (PD, n=24) and in twenty healthy controls (control group,n=20).Serum level of 1，25-(OH) 2VitD was measured by enzyme immunoassay(EIA).Serum intact parathyroid hormone (PTH), creatinine, and calcium and phosphorus were also measured.Results: Serum FGF-23 was obviously higher in HD group（\[88.51±35.01\] ng/L vs \[11.76±3.63\] ng/L）and PD group（\[87.85±33.65\] ng/L vs \[11.76±3.63\] ng/L）than in control group. Moreover, the serum level of 1，25-（OH）2VitD was lower in HD and PD groups than in control group (\[19.82±4.99\] pmol/L vs \[48.37±3.47\] pmol/L; \[24.31±7.11\] pmol/L vs \[48.37±3.47\] pmol/L ), and the level of 1，25-（OH）2VitD was much lower in HD group than in PD group. Pearson relativity analysis showed that serum FGF-23 level was positively correlated with serum creatinine, phosphorus, intact PTH and duration of dialysis(P<0.01); and was negatively correlated with 1，25-（OH）2VitD(P<0.01). Conclusion: Serum FGF-23 is greatly up-regulated in patients with ESRD, and the level of serum 1，25-（OH）2VitD is down-regulated. The changes of FGF-23 is associated with serum creatinine, phosphorus, intact PTH and 1，25-（OH）2VitD.