Abstract: In this paper, various moist potential vorticities with different definitions are theoretically analyzed and numerically diagnosed based on the simulation of typhoon Mujigae (1522). The results show that the differences between the equivalent potential vorticity, the generalized moist potential vorticity and the modified moist potential vorticity are mainly caused by the potential temperature that is defined differently. An additional variable with explicit water vapor is added to the conventionally defined potential temperature. The equivalent potential vorticity, the generalized moist potential vorticity and the modified moist potential vorticity can be divided into two parts: the dry component and the moist component. The dry components of these moist potential vorticities are the same as the Ertel potential vorticity and implicitly contain the effect of latent heat in phase changes. The essential difference between these moist potential vorticities is reflected in their moist components, which can explicitly contain the effect of water vapor. Based on simulation results and diagnostic analysis of these vorticities in the typhoon process, it is found that the distribution of the modified moist potential vorticity is like a “hollow tower” and the high value area is located inside of the eye wall, which is very similar to that of the Ertel potential vorticity. And the distribution of the moist component of the modified moist potential vorticity is also very similar to that of the equivalent potential vorticity, but the absolute value of the former is smaller. These results indicate that the modified moist potential vorticity can maintain the characteristics of the original Ertel potential vorticity. It can not only reflect the structure and intensity changes of the typhoon but also reflect the influence of water vapor distribution reasonably. As shown above, the modified moist potential vorticity has a potential application for the diagnosis and forecast of typhoons. The value of the equivalent potential vorticity is negative in the low level, which is largely related to the distribution of water vapor gradient. Note that the equivalent potential vorticity doesn’t have a good matching relationship with vertical velocity, latent heating and other factors, which limits its application in analyzing the typhoon structure and evolution. The generalized moist potential vorticity has a complex form and only has some diagnostic advantages in nearly saturated condition.