Abstract: AIM To observe the inflammatory reaction of 90A consistency, softsegment modified PU and pure PU, which were assembled into a ventricule assisted device (VAD). METHODS The animal left ventricular experiment models were established with canines and VAD, which was made from hardsegment modified PU (group A), soft segment modified PU (group B) and pure PU (group C). At different time points, histological changes were observed and inflammatory factors tites including IL6, IL8 and TNFα were measured. RESULTS Group C had the worse inflammatory reaction compared with Group A and B. The levels of inflammatory factors of IL6, IL8 and TNFα showed a light rising tendency within 48 hours and were higher in group C than those in group A and B (P<0.05). The levels of these inflammatory factors stayed in a stable level after 48 hours of assisted circulation. CONCLUSION Hardsegment modified PU has only milder inflammatory reaction but better haemocompatibility than those of pure PU and can be the first choice of VAD material for wide application.