Based on the mesoscale WRF model, the present study analyzes the development and evolution characteristics of multi-scale vortices in the middle and lower atmospheres of an ideal tropical cyclone under the assumption of no background airflow environment. The precise scale separation is based on Fourier transform, and the original vorticity field is divided into three scale ranges including system scale (greater than 150 km), intermediate scale (50~150 km), and convective scale (less than 50 km). The results show that the non-axisymmetric structure of the tropical cyclone is mainly caused by the movement on intermediate and convective scales. Moreover, the evolution characteristics of the intermediate-scale vorticity correspond well with the phases of tropical cyclone intensification, especially the rapid intensification phase. The full-scale vorticity budget feature is mainly manifested as offset effects, i.e., STR/HAD and TIL/VAD, and the net contribution of the former is significantly stronger than that of the latter. The features of the system-scale vorticity budget and the full-scale vorticity budget are basically the same, but the intermediate-scale vorticity budget shows distinctive characteristics: before the integration of 70h, the contribution of each budget item is opposite to that on the system scale, and afterwards, the sign transition of the items is the same as that on the system scale; however, the net contribution of the income and expenditure items is significantly larger than that on the system scale. In general, the rapid increase of the simulated ideal tropical cyclone with the horizontal resolution lower than 5km is mainly related to the rapid increase of the net contribution of STR / HAD on the intermediate scale. Furthermore, we further study the spatial evolution of the intermediate-scale vorticity budget items during a specific period. The results show that during the intensification stage of the tropical cyclone, each budget term plays a non-negligible role in the axisymmetricalization of the vortex core, and TIL plays a leading role when the abnormally negative vorticity in the center decays and finally becomes a positive vorticity. [ABSTRACT FROM AUTHOR]