Abstract: The surface of carbon fiber (CF) is chemically inert, resulting in insufficient interfacial wettability between CF and polyphenylene sulfide (PPS) matrix, resulting in weak interfacial bonding strength, which seriously restricts the application of carbon fiber reinforced polyphenylene sulfide (CF/PPS) composites as main load-bearing structural components. Based on the principle of phase inversion emulsification, polyethersulfone (PES) was emulsified to prepare PES water-based sizing agent to strengthen the interfacial bonding between CF and PPS matrix. By characterizing the physical and chemical structure of the surface of CF after sizing, and combining with the macroscopic mechanical properties test, the influence mechanism of PES water-based sizing agent on the interface was systematically discussed, and the enhancement mechanism of PES water-based sizing agent to improve the performance of CF/PPS composites was clarified. The results show that PES water-based sizing agent can effectively improve the interfacial bonding between PES and PPS. The mechanical properties of CF/PPS composites after sizing modification increase first and then decrease with the increase of PES sizing concentration, and reach the maximum at 0.5wt% PES concentration. Compared with the CF/PPS composites after desizing treatment, the interlaminar shear strength increases by 52.5%, and the flexural strength and flexural modulus increase by 43.3% and 7.9%, respectively.