A novel technology to measure oil concentration in water is presented, and mie-scattering theory was creatively introduced to oil-in-water detection in the present study. A variety of oil samples were examined to obtain both scattering and infrared absorption spectra, and the linear correlation between light scattering intensity and measures with infrared spectrophotometry is more than 0.98. In addition, compared to the conventional methods, light scattering method requires no chemical reagent, and it is suitable for in situ measurement of oil in water.