Abstract: Healing processing of 16Mn steel samples was carried out. The healing area of internal cracks made by compressing a drilled hole was observed and analyzed. SEM analysis displayed that the fine structure in the healing area is mostly ferrite and there exists many polyangular grains of several hundreds nanometer. Vickers hardness tests showed that the hardness of ferrite in the healing area is higher than that in the matrix, which may result from strengthening of polyangular grains.