Objective To access evaluate the efficacy and safety of on-line hemodiafiltration for treating a-cute cerebrovascular disease (ACVD) patients complicated with hyperosmolar nonketotie diabetic coma (HNDC).Method Totally 11 patients of ACVD complicated with HNDC were observed for this prospective control study.All of them underwent on-line hemodiafiltrafion for 90 minutes using Fressnius 4008S Hemodialysis Machine withONLILNEplus TM and F60 one hour after final diagnosis was made. The bicarbonate ultrafiltrate rate was set at 500ml/min and blood flow at 150 ～ 180 ml/min; and the substitute fluid were infused with post-dilution at 50 ～ 60ml/min. The symptom of brain edema and cardiac insufficiency during the same course of treatment was observed.Blood were taken from the patients to detect serum kalium, serum glucose, serum natrium, BUN and plasma os-motic pressure at one hour before treatment and six hours after treatment, respectively. The change of in conscious-ness and adverse effects were evaluated at 24 hours after treatment. Results All patients were treated successful-ly. The blood glucose, serum natrium, serum kalium, BUN and plasma osmotic pressure were decreased after on-line hemodiafiltration. Among the 11 patients, consciousness was improved obviously in 8 patients, 3 patientsdied, accounting for 73% of successful effectiveness. Conclusions The on-line hemodiafiltration was effectiveand safe for treating ACVD patients complicated with HNDC.