"Self-healing effect" is one of the important phenomena in laser metal direct forming (LMDF) process, and plays an important role in improving the forming quality of parts under open-loop control. In order to study the self-healing ability of different materials, reveal main influencing factors, and provide guidance for formulating correct forming process to improve the forming precision, orthogonal experiment is designed to fabricate several thin-walled parts on substrate with "convex" characteristics in LMDF, and the influence of process parameters on sample dimension is analyzed. The experimental results on 316 L stainless steel show that the influence of different process parameters on the self-healing ability varies significantly: the traverse speed is the most important factor, the laser power next, and then the powder mass flow rate. The 316 L stainless steel self-healing ability can be improved remarkably when using optimized laser power, traverse velocity, and powder mass flow rate as 240 W, 6.0 mm/s, and 7.3 g/min, respectively. The maximum self-healing height exceeds 1.54 mm and the self-healing rate is 0.038 mm per layer.