Strength analysis of the coupling rod working in curve condition for radial bogie mechanism was provided. Firstly, through the mechanics simplified model of DF8B diesel locomotive’s radial bogie, formula of coupling rod’s loads in the curve condition was deduced. Then, the dynamic model of DF8B diesel locomotive was modeled by multi-body dynamic software SIMPACK and the theoretical formula was verified by the simulation results. On this basis, the impact of operation curve radius, outer rail super elevation, speed, track irregularity and the structural parameters on the coupling rod’s loads was studied. The results showed that: when the locomotive’s speed increased 20 km/h, rod’s loads increased by about 25~30 kN; when rod’s offset increased approximately 10% and 20%, respectively, rod’s loads were reduced by 8.8% and 16.5%.