Abstract: Segmented polyether urethaneureas (SPEU-W) were synthesized from 4, 4'-diphenylmethane diisocyanate (MDI), polytetramethylene glycol (PTMG, M_n=1100) and water as chain extender by two-step solution polymerization. The physical properties and anticoagulant activity of the polymers prepared were measured. The experimental results showed that the extent of phase separation and the anticoagulant activity of SPEU-W were almost the same as those of polyether urethaneureas based on MDI, PTMG and ethylenediamine chain extender and better than those of polyether urethanes based on MDI, PTMG and butanediol chain extender.