【Abstract】 Objective To research dialysis patients haemodynamics change who often intradialytic hypotension by measured the effective circulating blood volume (CBV)、cardiac output（CO）and peripheral vascular resistance (PVR) with Ultrasound dilution method. Methods we measured 20 patiernts about the changes of center blood volume、cardiac output、cardiac index（CI）and peripheral vascular resistance before and after haemodialysis who often intradialytic hypotension by HD02 Haemodialysis monitor during haemodialysis session.Further we compare the changes of those index when we give high concentrate dextroglucose、 metrazol and adjust patients’dry weight respectively. Results the decisive factor of intradialytic hypotension are changes of CBV（ΔCBV） and CO（ΔCO） (P ＜ 0.05), though the changes of PVR has also increase, but has no significant difference (P ＞0.05).When we compare the change between high concentrate dextroglucose and metrazol,we get the result that the former can increase CBV and CO significantly, have significant difference in ΔCBV[(0.04±0.06) V (0.11±0.04) P＜ 0.05） and ΔCO （0.33±0.15 V 0.70±0.16 P ＜ 0.05）. 3hΔCO have significant increased (-1.63±0.68 V -0.91±0.34 P ＜ 0.05）at haemodialysis 3 hour after adjust dry weight. Conclusions The decisive reasons of intradialytic hypotension are reduction of effective circulating blood volume and cardiac output ,but not PVR and myocardial reserve. Ultrasound dilution is a simple、non-invasive method to monitor cardiac function during haemodialysis session and supply evidence for intervening treatment. Ultrasound dilution can also be applied for prevetion of intradialytic hypotension.