Abstract: Ultrasonic testing and color penetrant testing were used to confirm the suspected lateral defects on the weld surface of the dissimilar steel Q235B and 304L in the pump tower area found in the visual inspection. The macroscopic fracture analysis combined with the color penetrant inspection has further verified the findings. The crack attributes and distribution characteristics of the transverse defects were analyzed; the cause of the crack initiation was preliminarily analyzed using PMI (material metal composition identification-spectral analysis method) data.