Abstract: A medical dilution tank experienced leakage during use. The causes of the leakage in the dilution tank were analyzed by macroscopic observation, chemical composition analysis, energy spectrum analysis. The results show that improper use of the inner layer material in the dilution tank resulted in a decrease in its resistance to chloride ion stress corrosion. Under the action of NaCl solution, stress corrosion occurred in the inner layer of the dilution tank. The tank body was not annealed to eliminate welding thermal stress, led to the formation of cracks around the weld seam, and ultimately caused leakage accidents in the dilution tank.