Abstract: With the stress-reorientation of hydrides considered, the theoretical models were given for the hydrogen-diffusion-induced multi-field coupling behaviors in zircaloy cladding tubes. The corresponding multi-field coupling computational methods were developed and the finite element procedures were obtained. For an axially-cracked cladding tube subjected to internal pressures, the finite element model was established to calculate and analyze the hydrogen-diffusion-induced multi-field coupling behaviors. The research results indicate that for a cracked cladding tube initially containing plenty of hydrogen atoms in solid solution, only considerable amount of hydrides precipitate around the crack tip, which mainly results from the high hydrostatic stress gradients and concentration gradients of hydrogen in solid solution there, together with lower terminal solid solubility; The majority of hydrides at the crack tip precipitate along the radial orientation, which will induce occurrence of radial cracking of cladding tubes to threaten their safety; After applying the internal pressures, due to the expansion strains induced by hydride precipitation, the hoop stress, the radial stress, the hydrostatic stress and its gradient will decrease with time, which results in a lower velocity of hydride precipitation.