Abstract: Cuprous oxide was prepared with copper sulfate and glucose under ultrasonic condition ，the polypyrrole - cuprous oxide composites were synthesized by using in-situ polymerization of pyrrole and cuprous oxide with ferric chloride as oxidant. Some factors that influenced the degradation of methyl orange catalized with polypyrrole - cuprous oxide composites were studied. The results indicated that the photocatalytic degradation rate of methyl orange was up to 95. 23% when the composites amount was 0.10g，the methyl orange initial concentration was 20mg/L，the illumination time was 2h，the solution pH of methyl orange solution was 9 to 10. The infrared spectra showed the characteristic absorption peak of polypyrrole were at 3433.36、3319.55、3003～3077 and 1655.15cm^-1，which is consistent with reports.

Key words: polypyrrole(PPy) , cuprous oxide(Cu₂O) , composites , visible light , photodegradation , methyl orange