A novel macro-RAFT emulsifier was synthesized with S, S’-bis(α, α’-dimethyl-α”-acetic acid)-trithiocarbonate (BDATT), M13-10 (self-made emulsifier) and acrylate monomer, which was further used to prepare surface sizing agent. On the other hand, M13-10 was synthesized with iso-tridecanol polyoxyethylene ether, sodium methoxide and sulfamic acid as the starting materials. The hydrophilicity of macro-RAFT emulsifier and the performance of surface sizing agent were affected by BDATT used as the chain transfer agent and M13-10 as the hydrophilic monomer. So, the CMC and HLB of the emulsifier prepared with different M13-10 content and BDATT content, were compared, as well as the particle size of the prepared surface sizing agent, and the cobb, bursting resistance, tensile resistance, folding endurance and roughness of paper sized. The results reveal that surface sizing agent with macro-RAFT emulsifier of which the amount of M13-10 is 7 w% and the amount of BDATT is 2.5 w% demonstrates the best sizing effect on paper with the contact angle of 119°, the surface water absorption (cobb) of 48.8 g/m 2 , the bursting strength of 285 kPa, the folding endurance of 19 and the tensile strength of 59.6 kN/m.