Toxicity reseach of nano materials not only has very important significance to human health, but also concerns labour protection and resource utilization etc., so it should be highly regarded by our government. This article overviews it from medicine, and expounds the significance of the toxicity estimate for nano materials according to the change of physico-chemical property after macroscopic materials be made to nano materials, it proposes that we should not ignore the potential influence on health and the necessity of investigation in the development of nanotechnology ,so that people can exactly recognize and reasonably utilize nano materials.