Abstract: A heavy rainfall event occurred in Shandong Province on 26-28 August 2004, it was caused mainly by Typhoon Aere (2004) and cold air, and the development of the inverted typhoon trough was closely associated with the intensification of the low-level jet and the transportation of heat and momentum from the typhoon low. Numerical simulation for this event is performed using the non-hydrostatic, two-way interactive, triply nested grid mesoscale model MM5 and the structure of the inverted typhoon trough is studied. Furthermore, the formation and development mechanism of the inverted typhoon trough as well as the meso-scale vortex are discussed through the budget of vorticity equation. The results show that the heavy rainfall is triggered by the strong convergence between the strong wind area and weak wind area within the inverted typhoon trough. Dynamic effects of the low-level jet, as well as the diabatic heating of precipitation play important role in the development of the inverted typhoon trough and the meso-scale vortex. Analysis of vorticity equation suggests that the divergence term in the low-troposphere, and the horizontal advection term and convection term in the mid-troposphere are the main contributors of positive vorticity. In addition, the effect of divergence term and advection term is opposite to each other. In the mid-troposphere, the vertical transportation term is positive and the tilting term is negative. The tendency of vorticity is the net result of their counteraction. However, the distribution of vorticity tendency on pressure level is not uniform. A strong positive voricity tendency is located in the southeast of the meso-low, which is the reason why the heavy rainfall occurred there. The horizontal convergence leads to the increase of positive vorticity in low levels, and the transportation of vorticity from low levels to high levels results in the increase of positive vorticity in high levels. Therefore, the development of the inverted typhoon trough and the formation of the meso-scale vortex are mainly caused by the vorticity generating in the low levels, and the vertical transportation of vorticity from the mid and low levels.