Reversible addition-fragmentation chain transfer polymerization (RAFT) is an effective controlled/living free radical polymerization method. It is widely used in the preparation of functional polymers. The key to RAFT polymerization is to select the appropriate RAFT agent. The preparation of water-soluble RAFT agents is critical based on environmentally sound and non-hazardous requirements. The paper introduces the mechanism of RAFT polymerization and summarizes the preparation and application of water-soluble RAFT agents. The mechanism of water solubility of RAFT chain transfer agent was discussed. On the one hand

the role of polar group

on the other hand

the role of ionic bond hydrogen bond etc. that has certain enlightenment for the preparation of water-soluble RAFT agent. The macro-RAFT agent often contains hydrophilic groups and hydrophobic groups with dispersion effect. Under the aqueous phase condition

not only a narrow molecular weight distribution block copolymer can be prepared by chain extension reaction

but also micro/nano-gel can be prepared.