Abstract: Based on the analysis of the Empirical Mode Decomposition (EMD) method, an improved algorithm for signal processing in IR optical gas detection is presented. It decomposes only frequency-modulated signal without need to decompose every Intrinsic Mode Function (IMF) component. Compared with the methods of low-pass filter and digital lock-in amplifier, the improved algorithm has advantages of short data set, fast computation speed and less signal energy loss. It is more effective and time-saving than the conventional EMD method. The changes of gas concentration can be diagnosed by the algorithm and the precision can be improved at the same time. Thereby the gas concentration can be determined accurately and efficiently and it is suitable for real-time detection.