A distributed feedback(DFB) laser with central wavelength of 1.330 μm is employed as the light source combined with wavelength modulation harmonic detection techniques and long optical-path techniques to in situ monitor HF gas concentration in industral situation.The system′s stability is analyzed with Allan variance.The nonlinear least square method and the pulse-proof moving averaging filter are selected to eliminate the outside influence.Long-term test results demonstrate that the developed system has the advantages of real time,continuous,non-contact and fast monitoring,and it possesses the capability of large scale and distributed remote monitoring.It satisfies different requirements for online monitoring of industrial HF and other gas fugitive emissions.