A mathematical model which described the hydrogen diffusivity near blunt crack tip was proposed. Coupled calculation model for structure and hydrogen diffusion analysis were put forward. Using finite element, the relations between hydrostatic pressure, plastic deformation and hydrogen diffusion were revealed. The synergy influence rules of plastic deformation and hydrogen near the crack tip were analyzed. Finite element method was used to evaluate the large deformation elasto-plastic behavior of the material with the hydrogen diffusion analysis results. Finite element analysis was employed to solve the coupled boundary-value problem of large strain elasto-plasticity and equilibrium hydrogen distributions near blunt crack tip by taking into consideration the effect of hydrogen on local flow stress. 