Abstract: The calculation based on the first proliferation formula of Einstein and the settlement formula semi-quantitatively and quantitatively indicates that the nano-particles' settling velocity is about one thousandth of micron particles'. This feature makes nano-particle more easily suspend in the atmosphere and solution and be absorbed by organisms through respiratory and circulatory system. Meanwhile, the calculation based on the interaction potential energy formula caused by Vander Waals force semi-quantitatively indicates that nano-particle is easier than micron particle to be adsorbed, aggregated and collected into the body from the food chain through transformation in the atmosphere or migration in water and soil. Therefore, nanoparticle has more serious toxicity and worse effect on organisms than micron particles. Finally, according to the research on the toxicity of nanomaterials, new direction to the virtuous development of nano-technology is proposed.