A pressure measurement and compensation technique was studied by employing a 3.291 μm Continuous Wave (CW) Interband Cascade Laser (ICL) and a dense-patterned Multipass Gas Cell (MPGC) with an effective optical path length of 54.6 m. The pressure inside the MPGC was measured based on direct Lorentzian absorption line fitting on the measured absorption spectral signal of CH4, and then pressure compensation was made on the masured CH4 concentration. Pressure calibration was performed from 1.33×104 Pa to 10.64×104 Pa using a 2.1×10-6 CH4 sample. An Allan deviation analysis of the measured pressure of a 2.1×10-6 CH4 at 9.31×104 Pa pressure indicates a measurement precision of ~219.5 Pa with a 2.2 s averaging time. Fiveteen groups of pressure/concentration measurements of 1.0×10-6, 1.2×10-6, 1.4×10-6, 1.6×10-6 and 2.1×10-6 CH4 samples at different pressures of 1.33×104, 3.99×104 and 6.65×104 Pa were performed, and the results proved the feasibility of the proposed pressure measurement and compensation technique.