In this paper, based on the subnet abstraction mechanism, a fluid-based large-scale bandwidth-limited worm simulation model is proposed. In this model, the fluid simulation paradigm is leveraged to take away the huge volume of scanning traffic to reduce the requirements of computational capability and memory usage. Through extensive comparisons with the packet-level worm simulation and the measurement datasets, experiments demonstrate that the proposed simulation model is capable of high fidelity and low resource consumption, and thus, can fulfill the needs of the analysis of bandwidth-limited worm propagation characteristics and the verification of worm defense strategies.