The problems of baseline drifting and distortion of mixed gases infrared spectra in the application field and the uncertain choice of the Rubberband′s piecewise quantity were discussed. In the situation of the spectrometer resolution of 4 cm-1 and mid-infrared band for the hydrocarbon gases, the baseline estimation and correction would be more ideal in the case of the piecewise quantity was set in the 50-120 and piecewise cubic Hermite interpolation method was selected to fit the baseline points by the ergodic method. For the problem of absorption points，which was mistaked as the baseline points, first of all, the obvious absorption points within the segment were eliminated by the method of the median and deviation. And then, the baseline points were selected by the partial least square method and certain threshold was set in the residual baseline points. Lastly, the selected baseline points was used to estimate the baseline by piecewise cubic Hermite interpolation method in the whole band. From the baseline correction result of the measured spectra, the provided method was simple and fast, and also suitable for on-line continuous analysis applications.