In this paper, a method to simplify a model in 3D environment is presented. The simplified model is achieved by finding the boundary box of the sub-division of the model, while the size of each sub-division is optimized using Tribes-D Particle Swarm Optimization. With this approach the complex 3D model can be simplified with a predefined level of detail. We demonstrated this approach on a pump model and compare it with other simplification method.