Aim The effect of polysaccharide of spirulina on mouse myelosuppression induced by cyclophosphamide was studied.Methods Mice in the model, treatment groups Ⅰand Ⅱwere given cyclophosphamide (ip 100 mg?kg-1) for there days.At the same time mice in the treatment groups Ⅰand Ⅱ were given ig spirulin 30 mg?kg-1 and 60 mg?kg-1 for ten days, while mice in the control group and model group were given ip 20 mg?kg-1 of NS.Peripheral blood and marrow cytometry, micromcelsus and chromosome aberration were analyed.Results In the dosages of 30 and 60 mg?kg-1 polysaccharide of spirulina,the polysaccharide of spirulina had perfect action on the perihemateikon and the function of bone hematoplast induced by cyclophosphamide (P