Abstract: The thin-shell tap was fabricated using new process of low-energy laser welding, instead of the traditional casting process which had high pollution and high energy-consuming. The corrosion resistance of the 304 and 310s stainless steel was investigated in boiling sulfuric acid and acid at room temperature, respectively. The microstructure of weld beam and fusion zone during corrosion process was observed by in-situ tracking method. The results showed that corrosion resistance of 310s stainless steel is better than that of 304 stainless steel. With the time increasing, grain boundaries of the fusion line do not widen obviously. Microscopic features of the fracture were dimples, which is indirect proof for its good corrosion resistance. Analysis indicated the chemical compositions in weld metal are close to that in the base metal. Cr content in corrosion ditch fell to 20.81%, but still more than 12%, ensuring the excellent corrosion resistance.