A novel method of Non-dispersion Infrared (NDIR) based on correlative technology for measuring CH₄ trace gas and its application in the field measurement are described in the paper.Because of low concentration and weak absorption,atmosphere methane detection with Non-dispersion Infrared (NDIR) system faces the problem of high noise interference.To improve detection ability,Gas Filter Correlation (GFC) technique is put forward to reduce background noise.Correlative technology plays an important role in detection of feeble signal.The method is based on the gas characteristic absorption in infrared region and the correlation operation principle.Feeble spectrum signal is modulated and detected by combining advanced Gas Filter Correlation (GFC) technique and correlation technique.Methane is detected in real time and fast.Experiment results show that the system detection precision can reach 10ppb.