In this paper, a novel reactive fatty alcohol ether sulfosuccinate emulsifier (RAEOSS10‐9) was polymerized into macromolecular emulsifier RAFT‐PRS through reversible addition–fragmentation chain transfer (RAFT) polymerization, and then RAFT‐PRS was co‐polymerized with monomers to form anionic surface sizing agent. The structures of RAEOSS10‐9 and RAFT‐PRS were characterized by Fourier transfer infrared spectra, and the RAFT polymerization activity of RAFT‐PRS was verified by gel permeation chromatography. The effects of RAFT reagent and RAEOSS10‐9 content on the properties of sizing emulsion and sizing paper were investigated. The morphology of latex particles and sizing paper surface were observed by use of scanning electron microscope and atomic force microscope. The water resistance, bursting resistance and folding resistance of sizing paper were studied. The optimal formulation of sizing emulsion was built according to the above results. Besides, the investigation of the mechanical properties suggests that proper amount of reactive emulsifier is beneficial for enhancing the stability of emulsion and the performance of paper. The RAEOSS10‐9 displays better emulsifying properties than imported emulsifier SR‐10, and the emulsion produced by RAEOSS10‐9 display more excellent application properties.