Abstract: Silver carbonate ultrafine powder was prepared with silver nitrate and sodium carbonate Under the condition of ultrasonic dispersion，and polypyrrole - silver carbonate composites were sythsized with ammonium persulfate as the oxidant in situ polymerization. The performance of the composites were detected with IR ，XRD and Laser particle size analyzer. Methyl orange was degraded with the composites as the catalyst under simulated natural light. When the dosage of the composites was 0.4g，the initial concentration of methyl orange solution was 10mg/L，the degradation time was 2.5h，the pH value of methyl orange solution was 6.0，and temperature was 40℃，the degradation rate of methyl orange was up to 98.43%.

Key words: polypyrrole, silver carbonate, composite materials, photocatalytic degradation, methyl orange, degradation rate