Simulation of wildfire spread remains to be a challenging task. In previous work, a cellular space fire spread simulation model has been developed based on the Discrete Event System Specification (DEVS) formalism. There is a need to improve simulation performance of this model for simulating large scale wildfires. This paper develops a partialmodular implementation of the DEVS-based cellular space model that eliminates the large number of inter-cell message exchanges for improving simulation performance. Both the modular and partial-modular approaches are presented and experiment results are provided. The results show that the partial-modular implementation can significantly improve simulation performance of the cellular space wildfire spread model.