In this study, a homogeneous cation exchange membrane with fluorocarbon backbone, i.e., P(VDF-co-CTFE)-g-PSSA membrane, was prepared by uniformly grafting sodium styrenesulfonate (PSSA) onto poly(vinylidene trifluoride-co-co-co-fluoroethylene) copolymer P (VDF-co-CTFE) by atom-transfer radical reactive polymerization (ATRP) reaction. Fourier-transform infrared spectroscopy (FT-IR), X-ray energy spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and contact angle measurements were used to characterize the P(VDF-co-CTFE)-g-PSSA prepared at different reaction temperatures, reaction time, and catalyst-to-ligand molar mass ratios. The results show that styrenesulfonic acid groups were successfully grafted on the fluorocarbon backbone structure, and the prepared cation exchange membrane has good thermal stability and mechanical properties. The scanning electron microscopy images show the phase separation morphology on the surface of the cation membrane; the cation membrane prepared by reacting at 130 ℃ for 7 h has a water absorption of 80.02%, a swelling rate of 8.89%, an ion-exchange capacity of 4.54 mmol/g, and an electrical conductivity of 0.50 mS/cm. The cation exchange membrane prepared in this study has application value in high salt wastewater treatment.