Welding is a main joint way of the alloy constructional steel. The welding heat affected zone (HAZ) is more sensitive to corrosion in comparison with other areas. In order to increase the corrosion resistance of the welding HAZ, laser surface quenching is used to treat the welding HAZ. According to the results of the orthogonal test, the optimized processing parameters are obtained. Based on the electrochemical analysis, it is found that the corrosion current of 30CrMnSi welding HAZ can be decreased obviously by laser quenching technology. So the corrosion resistance of the HAZ can be improved effectively with this method.