The experiments were aimed at obtaining crack healing of hydrogen attack (HA) in low carbon steel by heat treatment. It was observed by SEM that HA cracks experienced different healing effects. The results indicated that the HA cracks≤10μm length can be healed completely by cyclic heat treatment between room temperature and 1000℃. Five cycles totalling 10 hours were used. The studies performed showed that crack healing is controlled by diffusion and that the recovery kinetics depend on the plastic deforming energy Es arising from the growth of HA bubbles or cracks. These findings led to the conclusion that the critical condition for healing of bubbles or cracks is Es≥2γ/r (where γis the surface tension, r is the radius of bubbles or half length of cracks) provided the atoms of H, C, Fe can diffuse rapidly.