The use of fillers to enhance the corrosion protection of epoxy resins has been widely applied. In this work, CeO2 and Benzotriazole (BTA) were introduced into an epoxy resin to enhance the corrosion resistance of Q235 carbon steel. SEM results indicated that the CeO2 grains were rod-like and ellipsoidal in shape, and the distribution pattern of BTA was analyzed by EDS. The dynamic potential polarization curve proved the excellent corrosion resistance of the composite epoxy resin with CeO2 and BTA co-addition; and electrochemical impedance spectroscopy test (EIS) analysis indicated the significantly enhanced long-term corrosion protection performance of the composite coating. And the optimal protective performance was provided by the coating containing 0.3 wt.% CeO2 and 20 wt.% BTA, which attributed to the barrier performance of CeO2 particles and chemical barrier effect of BTA. The formation of corrosion products was analyzed using XRD. In addition, the corrosion resistance mechanism of the coating was also discussed in detail.