Abstract: The formula for calculating the maximum tensile stress of the specimen with weld was deduced in detail, when the specimen was loaded by four-point-bending (FPB) in the stress corrosion test. The new formula was compared to the formula listed in GB/T 15970.2-2000. The results showed that the influence of Young’s modulus and width of the weld on the maximum tensile stress was considered in the deduced formula. The real stress was reflected by the deduced formula. When the ratio between weld width and distance between external fulcrums was less than 0.423, the difference between real stress and calculated stress by the formula listed in GB/T 15970.2-2000 increased with the decrease of weld width and the increase of Young’s modulus difference between weld and base metal.