Worm validation experiments are very important for worm research. A major method to conduct these experiments is through simulation. However, almost all of the existing worm simulation models inherently face a rigid fidelity-scalability tradeoff problem. In this paper, we propose a multi-level fidelity-preserving worm simulation model aiming to solve this problem. Our model is composed of a set of different components, and the fidelity of every component can be adjusted to meet different fidelity-scalability tradeoff requirements by changing the abstraction level of the component model. Thus, the overall fidelity of the worm simulation model can be adjusted at a finer granularity, enabling the new model to flexibly trade fidelity with scalability, or vice versa, depending on specific requirements. In addition, we also present the methodology on how to construct the multi-level fidelity-preserving bandwidth-limited worm simulation model and how to use the model to validate the effectiveness of defense strategies.