Abstract: The organizational structures of high-chromium cast iron were changed by heat treatment, ultrasonic evaluation of the organizational structures were researched by three ways of ultrasonic velocity, spectrum analysis, energy spectrum analysis. The ultrasonic evaluation model of the organizational structure in high-chromium cast iron was established. The experiment results indicated that at the same quenching but different cooling rate, the martensite in the test parts under air cooling was maximum, so the speed of sound was also the lowest. However, under furnace cooling, it showed that the speed of sound was also fastest since the martensite was smallest. If increasing solution temperature, the amount of martensite was increased at first and then decreased, corresponding the ultrasonic velocity was reducing first and then increasing. The velocity of sound wave of annealed samples was smaller than the test parts without tempering, the consequence was caused by the changes in elastic modulus.