Diclofenac sodium is one of the new pollutants widely distributed in water, and its removal has attracted much attention. In order to improve the removal efficiency of diclofenac sodium and obtain cost-effective and environmentally-friendly adsorbents, the chitosan polydopamine modified hydrogel (CS-PDA) was prepared from chitosan by introducing polydopamine onto chitosan by photocatalytic method. The adsorption properties of diclofenac sodium were studied. The CS-PDA was characterized by SEM, FTIR, XPS and BET. The results showed that the CS-PDA had a network structure, porous structure and a specific surface area of 22.46 m²·g^-1. Explored the effects of time, temperature, initial concentration and pH value on the adsorption effect, the results showed that the adsorption capacity of CS-PDA was the largest at pH=4.3, the adsorption kinetics of CS-PDA for diclofenac sodium was in accordance with the pseudo second order kinetic model, and reached the adsorption saturation at 240 minutes.The adsorption isotherm was in line with the Langmuir isotherm model and the Langmuir theoretical maximum adsorption capacity of diclofenac sodium at 25 ℃ was 333.2 mg/g. The adsorption capacity of diclofenac sodium by CS-PDA was higher than 70 mg/g after 7 regeneration cycles.