Microcapsules containing potassium peroxydisulfate as the core material and polypyrrole as the shell material were prepared by in situ interfacial copolymerization in O/W microemulsion. The encapsulation efficiency of potassium peroxydisulfate reached peak at 95% in the microcapsules. The controlled release time of potassium peroxydisulfate could be at 3-14 h from the microcapsules. The kinetic model of the controlled release was zero-order kinetic equation at 40 degrees C.