A new method is introduced to real-timely monitor the pollution gas discharge of chemical plant.The method is called Fourier Transform Infrared Spectrometry based on the Solar Occultation Flux technique(SOF-FTIR).A simplified model is also proposed to obtain background spectrum,measurement spectrum and atmospheric transmittance near the pollution gas.Measurement spectrum is obtained by continuously measuring the contaminated areas at a closed-loop manner.And density column of pollution gas is achieved by using the nonlinear least squares fitting algorithm (NLLS).Using this method，remote sensing experiments of SO2 discharge around a chemical plant were made.Compared with traditional FTIR methods,this method is featured with convenient operation and high maneuverability,so it has a good application prospect in pollution monitoring and other contingency measurement applications.