Considering the gaseous cavitation rate is influenced by local pressure, a transient gaseous cavitation model is developed from an equilibrium gaseous cavitation model in consideration of transient gaseous cavitation theories and the Bunsen solubility. With the shear stress transport (SST) model with low-Re correction and air backflow from the bearing outlets, the transient gaseous cavitation model is applied to the three-dimensional simulations of an entire tilting-pad journal bearing at 3000 rpm speed and under 180 kN load. The simulated bearing pressure and load are in good agreement with the experimental data, indicating that the transient gaseous cavitation model performs well in the bearing simulations. Based on the comparisons of the simulated air and dissolved air distributions between the transient and equilibrium gaseous cavitation models, the simulated cavitation process of the transient gaseous cavitation is proved to be not in equilibrium and mass transfer occur between the backflow air and oil. The purpose of building the transient gaseous cavitation model is thus met. Analyses of the air distributions indicate that high cavitation rates and low dissolution rates makes air volume a major part of the total air volume and close to the physical gaseous cavitation process.