Abstract: 6.1 nm PbSe QDs of uniform size and regular arrangement have been synthesized by coordination solvent method,and a new type of near-infrared (NIR) light source of PbSe quantum dots (QDs) has been developed in this paper.The NIR PbSe QDs light source reached an absorption peak at 1862nm and a PL peak at 1943nm.The PL spectrum of NIR PbSe QDs light source covered the entire absorption spectrum of NH3 gas (from 1900 to 2060nm).Its photoluminescence(PL) spectrum was narrow,and the corresponding filter could be omitted.But it is necessary to increase the filter in order to match the gas absorption peak of corresponding band,because the spectral bandwidth of traditional infrared light source is wider.Based on NIR PbSe light source,the experiments of detecting different concentration of NH3 have been carried on.The experimental results show that the lowest detection limit of 5×10-5 and the detection error of 2% can be obtained in the new detection system.It proves that the new detection system has very good measurement results and possesses the basis of application in gas detection.