A simulator is designed to explore the interactive mechanism of a plasma jet with the liquid medium in the bulk-loaded liquid electrothermal chemical launching process. The properties of the plasma jet expanding in the liquid and the mixing characteristics of the plasma jet with liquid in the cylindrical chamber are studied using a high speed camera system. According to the experimental results, a two-dimensional axisymmetric unsteady compressible flow model has been proposed. The transient characteristics of the jet in flow field have been simulated. The results indicate that, during the expansion of the plasma jet in the liquid medium, there is relatively strong turbulent mixing. The interface between the two phases is not smooth and fluctuates with time stochastically. The higher the discharge voltage is, the stronger the Helmholtz instability effect will be. The Taylor cavity forming during the jet expansion can be divided into three regions: the main flow region, the compression region, and the backflow vortex region. In the main flow region the temperature and velocity of the plasma jet are relatively high and both decrease along the axial and radial direction. The pressure near the Taylor cavity head is high. The high pressure region grows gradually while the pressure value decreases. The calculated axial expansion displacement of the Taylor cavity coincides well with the measured one from experiment.