The hydrogen embrittlement mechanism is one of long-term research topics of ultrahigh strength steels involving the microstructure optimization control. It is valuable to clarify what happens to the crystallographic lattice and the local crystal orientation just before brittle fracture during delayed loading, and why the brittle fracture stress decreases with the increment of diffusional hydrogen concentration. Our preliminary study of high strength steel (RB1120277) charged with 8ppm diffusional hydrogen and then coated with Zn protection film suggested that the neutron diffraction is feasible to be applied to hydrogen embrittlement study. Here, an experiment is planned to clarify the influence of diffusional hydrogen charging on the elastoplastic deformation behaviors, attempting to clarify such hydrogen induced brittle fracture phenomenon at high hydrogen concentration.