Abstract: Cold-welding technology has been applied to the engine remanufacturing field.In this paper, the surface defect of HT250 castiron used in diesel engine cylinder was repaired with inferior-laser instantaneous melting cold-welding technology.The cold-welding residual stress was measured through the X-ray diffraction method to study the regularity of residual stress and the relationship between the residual stress and different process parameters.The results show that the stress near the weld seam is tensile and the stress away from the weld seam is compressive.The cold welding residual stress distribution is quite narrow.The peak stress mainly distributes in the range of 5mm from the weld seam center and the residual stress is close to zero in the place of 20 mm away from the weld seam center.Time parameter has little influence on the peak stress while the energy parameter's influence is great.Through the change of time and energy, smaller residual peak stress can be obtained to meet the repair requirements for surface damage on engine remanufacturing parts.