Take Tian'e Longtan bridge with a main span of 600 m as an example, a real bridge beam-slab model was established by using the finite element software Midas/Civil,, arch rib depths h and arch rib thicknesses t on the peak stress of chords, concrete in tubes and concrete wrapped around them are compared and analyzed. Besides, combined with the overall design of the route, the overall stability of the whole bridge and the structural requirements of the main arch, the optimal combination of structural parameters of the main arch rib is finally obtained. Given other structural parameters, the results show that: (1) When the arch rib depth of this bridge is h = 8 ~ 12 m, its overall stability is obviously better than that of the arch rib depth h = 6 ~ 10 m and 7 ~ 11 m; (2) Under the same structural parameters of the arch rib, the peak stress of the bottom plate and the web is obviously higher than that of the top plate, and the sensitivity of the bottom plate thickness tb and the web thickness tf to the peak stress of the bottom plate and the web is obviously greater than that of the top plate thickness tu. It is mainly related to the pouring sequence of the outsourcing concrete, that is, the bottom plate is poured first, then the web plate is poured, and the top plate is poured last. The first pouring is the first stress, and the corresponding plate thickness also needs to be increased accordingly; (3) Considering the structural requirements of this bridge, the recommended top plate thickness tu is 65 cm. Considering the peak stress of this bridge, the recommended web plate thickness tf is 45 cm + 45 cm ~ 95 cm, and the bottom plate thickness tb is 65 cm + 80 cm + 80 cm ~ 130 cm.