Atom transfer radical polymerization(ATRP) is one of the most robust and versatile tools for the synthesis of well-defined polymers. The traditional ATRP have to be conducted with high concentration of metal catalyst to compensate for the unavoidable radical termination reaction. A series of ATRP variants have been developed to reduce the metal catalyst concentration to 100 ppm or below. However, the contamination of the metal residue still remains. Organocatalyzed ATRP(O-ATRP) provides a green and reliable route to functionalized well-defined polymer without metal residue. The development of organic photoredox catalyst system is the key point of O-ATRP. This review highlights the recent progress in O-ATRP, including the various organic photoredox catalyst systems and polymerization mechanism. Moreover, the applications of O-ATRP in polymer synthesis are discussed.