Abstract: Porous flame retardant cobalt stannate（CoSnO3） was prepared with SnCl4·5H2O and Co（NO3）2·6H2O as raw materials and activated carbon as template.The structure and morphology of CoSnO3 were characterized by XRD and SEM.Then CoSnO3 as flame-retardant and smoke suppressant for flexible polyvinyl chloride was studied.In case of the PVC con- taining 15 phr of CoSnO3，the LOI of PVC was increased to 35.6%，the SDR value was as low as 75.2%，elongation at break was up to 168.32%，and the tensile strength was 22.50 MPa.The thermal degradation behavior of PVC can be studied by the results of TGA.Thermal degradation temperature of the PVC/CoSnO3 sample was lower than neat PVC，and the amount of residual carbon was increased at high temperature.The results demonstrated that CoSnO3 can be used as a highly effective flame retardant for flexible PVC.

Key words: cobalt stannate, flame retardant, polyvinyl chloride