Cavitation is an important phenomenon in hydraulic engineering. In order to understand better the impact of the phase change rate on cavitation, both theoretical and numerical study are taken in this paper. On one side, theoretical analysis are carried out on Singhal full cavitation model and Kunz cavitation model. The results show that phase change time is much less than the flow time in cavitation. We get that cavitation is insensitive to phase change rate theoretically. On the other side, we apply the two cavitation models to simulate the cloud cavitation of axisymmetric body under different phase rates. The numerical results show that phase change rate has little influence on cavitation form within a certain range and thus verifies the theoretical analysis.