The stress change of deck-U rib joint weld in the steel bridge was studied considering different structural parameters. Meanwhile, the stress mechanism was also analyzed to compare the stress distributions of two different U rib structures. The stress gradient of the deck weld was extracted to investigate the law of stress change. After that, the fatigue stress distribution of deck-U rib joint weld under different structural parameters was analyzed. The result shows that cut U rib and full U rib can both reflect the mechanical performance of deck-U rib joint weld faithfully. The greater the deck thickness and penetration rate are, the smaller the stress of deck-U rib joint weld is. Therefore, increasing the deck thickness can improve the mechanical performance. Besides, the U rib thickness and weld leg size exert little influence on the stress of deck-U rib joint weld.