Based on digital image processing technique and optical scattering theory of particles,an optical measurement system for experimental investigation on instantaneous concentration fields of flows is presented.The system is characteristic of non-intrusion,full-field measurement,wide measurement region and cheap cost.It is directly applied to the environment wind tunnel in the University of Shanghai for Science and Technology.The results are demonstrated to show that the system is feasible and effective.The system has wide applications and it is useful for experimental investigation on fluidic flow,communication pollution dispersion,and street canyon pollution.