Objective To observe the clinical effect of interferon a-1b on chranic idiopathic thrombocytopenic purpura. Methods fifty-two patients were randomly divided into two groups, 32cases in the treatment group were treated with interferon a-1b, 20cases in the control group were treated with prednisone. to observe the clinical effect of two groups were treated.Results The percentages of complete effect, partial effect and total effect were 37.50%(12/32),31.25%(10/32),68.75%(22/32) in the treatment group. but 5%(1/20),20%)(4/20),25%(5/20) in the control group. There were significantly different betwen two groups of the complete effect and total effect (p<0.01). The treatment group has less adverse drug reactions, were treated easily.Conclusion Interferon a-1b is effective and safe for treating chronic idiopathic thrombocytopenic purpure, and deserved to be popularized.