A near forward light scattering experimental apparatus is designed to investigate the light scattering properties of airborne particles and its applications in measurement of dust mass concentration. By experimental measurement and the Mie scattering theory for both monodisperse and polydisperse particulate matter samples, the relationships between near forward light scattering intensity and particle diameter, size distribution are obtained. The results demonstrate that the experimental apparatus can be used to measure the aerosol mass concentration of airborne particles in ambient air. More accurate responsivity can be obtained through experimental measurement and the Mie scattering theory for known monodisperse aerosol samples, and it is possible to estimate the error range in measurement of ambient air particles. If calibrated with the ultrafine Arizona road dust, the mass concentration readings of urban aerosols should be corrected by multiplying a factor of 2.5.