Abstract: Three-dimensional model was established to simulate the transient hydrogen diffusion for X80 pipeline steel welded joint using ABAQUS finite element software. Based on the coupled thermo-mechanical-diffusion analyses under various welding conditions, the effects of welding parameters on the hydrogen diffusion behavior and distribution pattern were investigated. Simulation results indicate that the heat-affected zone with stress concentration was the part with both high-level residual stress and high hydrogen concentration in the welded joint. Increasing preheating temperature and heat input was favorable for hydrogen to diffuse out from the weld zone and effective in reducing hydrogen concentration in the heat-affected zone, which would reduce the susceptibility to hydrogen induced cracking.