To sieve a new type of polyether polyurethane as an injectable prosthetic nucleus pulpous through testing the cytotoxicity in vitro.Methods Five experimental groups were set as following:that samples 1,2,3 groups were polyether-polyurethane polymerized of different ratio of soft and hard segment with different catalysts; group 4 was polyether polyurethane polymerized slowly at 37 ℃ without catalyst; group 5was polyether polyurethane that toxic monomer responded completely.Additionally,a control group of culture medium was set without material extracts.Get 0.6 mg from each sample product and make into material extracts after disinfection,then dilution them by 50% and culture the mouse fibroblasts(cell L929)until 3 d,4d,5 d,by Adopting 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide(MTT)colorimetric method to compare the 490 nm OD between the materials and control groups obtained by enzyme linked immune analysis,calculate the RGR of cells,and then evaluating the cytotoxicity of the materials.Results The RGR of L929 cell in group 4 and group 5 have no significant difference compared to the control group.Cytotoxic levels were 0 to 1; difference of the RGR of L929 cell between group 1-3 and control group were statistically significant.Cytotoxic levels were 1 to 2,but the cell morphology was normal.Conclusion The material polymerized without catalyst does not show cytotoxicity,and has great potential to be used as a substitute for nucleus pulposus.The cytotoxicity of the materials polymerized with catalyst needs to be tested more.