Traditional dust sensor is low precision and its precision keeping is poor in case of out door using, to resolve these problems, a multilaser dust detection method is studied based on Mie light scattering principle and a dust concentration detection system is designed . The optical measuring principle of dust detection system is introduced, luminous flux and particulate concentration calculation method is studied, and parameters of the measuring system are optimized. Moreover, a multilaser dust detection system is designed and the relationship between light transmittance and dust thickness is analysis. Experiment is performed compared with national measurement point and PPD4NS dust sensor, the result show that maxim relative deviation of the new system compared with national measurement point is 8.5%, the measuring accuracy is improved greatly compared PPD4NS.