We used the OP-FTIR system organized by ourselves to monitor the methane concentration continuously,retrieved the concentration from the measured spectrum.Sample analysis of the experiment results is given in this paper.This experiment indicates that this system to monitor the trace element concentration has steady performance.The system does not have to contact the object gas when it is used.The experiment results can response the pollution information of measured region in time.So this system can satisfy the need of monitoring gas pollution in industry.