Abstract: The arc extinguishing nozzle density of five kinds of nozzle samples ranging in 93.84%～94.63% was quantitatively characterized with two parameters of ultrasonic velocity and amplitude spectral peak. The results indicate that the velocity and amplitude spectral peak increase with the nozzle density, the changing trend of the two indicators has good consistency with the density. This study demonstrates the feasibility of using ultrasonic testing technique to detect the density of nozzle, and also provides a practical quality control method for nozzle.