Abstract: This article focused on the cavitation phenomenon in the flow field of the conveying road,cavitation development process and mechanism analysis were carried out.The cavitation incipient criterion and the outflow restriction criterion based on the cavitation flow rate were compared.The influence of the test medium on the cavitation test were studied and verified by cavitation test.The results show that,compared with the cavitation incipient criterion,the outflow restriction criterion based on the cavitation flow rate is a more convenient and effective method for evaluating cavitation margin.This method has good applicability and strong testability.The cavitation flow coefficient of the outlet is determined by the structure and parameters of the outlet.Medium,pressure and temperature conditions have little effect on it,which means the medium substitution test is feasible.