Creating proper 3D models play an important role in the development of scene simulation system based on multigen creator and Vega software. However, it is very difficult to construct complex structures by multigen creator. In this paper, one approach is proposed utilizing 3dsmax assistant modeling software (we use 3dsmax as an assistant modeling software). 3D model developed in 3dsmax can be saved in .3ds file and then imported into multigen creator. The model is revised and then saved in .fit file of creator. To reduce model's data, simplification strategy is used in modeling process. The problem of constructing complex models in creator is solved smoothly. The models constructed by this method have good third dimension, small size, and could be driving by Vega correctly.