Abstract: Based on the quantitative comparison of ultrasonic testing, this paper studies the effect of welding technology on the ultrasonic propagation performance of 9Ni steel weld, and discusses the influence of the change of weld microstructure and grain size on the quantitative results of 9Ni steel ultrasonic testing. It provides a basis for optimizing the ultrasonic testing technology of 9Ni steel and improving the accuracy of ultrasonic quantitative testing of defects. In this paper, the quantitative comparison of ultrasonic testing results between flux-cored arc welding (FCAW) and shielded metal arc welding (SMAW) is made. The quantitative results of the same defects between the welds formed by two welding processes and the base metal are analyzed, and the causes of the difference in the testing results are discussed and summarized.