The present invention relates to a process for continuously preparing polymer by RAFT solution polymerization, the process comprising: introducing into a flow reactor a reaction solution comprising one or more ethylenically unsaturated monomers, RAFT agent, non-reactive solvent and free radical initiator; and promoting RAFT polymerization of the one or more ethylenically unsaturated monomers within the reactor so as to form a polymer solution that flows out of the reactor.