Abstract: This paper discusses time-variant simulation problems which exist in nature widely, and realizes a time-variant rendering method based on ray tracing.First, system reconstructs the surfaces of model by surfels, and sets surfels' properties values of model.Then system generates rays from ray source, and sets ray properties values.After shooting rays from ray source, system exchanges surfels' properties with rays' properties when rays hit the surfaces of model.After selecting suitable texture from texture array, Last, system renders the model again.The model could show time-variant procedure with this method.We verify this method in building scene.