Objective To explore the effect of upgrade of dialysate quality on the microinflammation in maintenance haemodialysis (MHD) patients. Methods Fifty-three MHD patients in Kidney Center of the First Affiliated Hospital,Medical College,Zhejiang University in January 2003 were enrolled in the prospectively study.The main end-points were survival at 8 years or weaning from haemodialysis during 8-year period including death, receiving renal transplantation or transferring to peritoneal dialysis.The endotoxin level of dialysate and patients' serum levels of interleukin-6 (IL-6),tumor necrosis factor α (TNF-α),C reaction protein (CRP),and albumin were recorded during the observation period. Results After the upgrade of water management system,endotoxin level of dialysate obviously decreased [(0.046±0.012) EU/ml vs (0.454±0.002) EU/ml,P＜0.01],and serum IL-6 [(3.947±3.624) ng/L vs (13.779±7.106) ng/L,P=0.036],TNF-α [(7.935±3.864) ng/L vs (12.804±8.017) ng/L,P=0.012] as well as CRP [(0.194±0.149) mg/L vs (0.561 ±0.309) mg/L,P＜0.01] decreased significantly,while serum albumin increased [(41.900±6.803) g/L vs (38.140±7.083) g/L,P=0.042].Hemoglobin level did not change significantly after the system upgrade,however,the dose of erythropoietin decreased [(93.0±12.7) U·kg-1·week-1 vs (131.0±10.1) U·kg-1·week-1,P=0.015]. Conclusions The upgrade of central dialysis fluid delivery and water management system by application of double reverse osmosis,high frequency heat disinfection and endotoxin filter can improve the quality of dialysate.Improvement of dialysate quality can ameliorate the microinflammation state of MHD patients.