Abstract: After corrosion in simulated South China Sea mud solution for 10, 24, 72, 120 h, the morphology and composition of the corrosion products on surface of the weld of X70 pipeline steel were analyzed by scanning electron microscopy and energy spectroscopy. Then the effect of corrosion product film on the corrosion behavior of the weld was studied by slow strain rate tensile tests and potentiodynamic polarization tests. The results show that with increasing corrosion time, the corrosion product films on surface of the weld were thickened. A dense corrosion product film was formed after corrosion for 72 h, and more pores and cracks were formed in the film after 120 h corrosion. With increasing corrosion time, the stress corrosion sensitivity of the weld increased first, then decreased, and then slightly increased. The electrochemical corrosion behavior showed the same change. After corrosion for 72 h, the formation of the dense corrosion product film reduced the stress corrosion sensitivity of the weld and improved the corrosion resistance.