Castor oil (CO) was introduced as a cross-linking agent into a water-based polyurethane (WPU) capped with pentaerythritol triacrylate (PETA), and the double bonds were cross-linked by ultraviolet light to construct a dual cross-linking system. CWPU coatings with different CO contents were prepared, and the effects of CO content on various properties of CWPU coatings were explored. The test results show that when the CO content is 4 %, the 24 h water absorption of the film is 4.5 %, the surface hardness is 2 H, and the adhesion to the Q235 steel plate substrate is 0. Subsequently, the anti-corrosion performance was tested and analyzed by polarization curve test and impedance spectrum test. The results showed that the protection efficiency of the CWPU coating with 4 % CO content on the Q235 steel plate substrate could reach 99.05 %.