Aimed at the problem that baseline drift or distortion often appears in Fourier transform spectra after spectrometer has continuously worked for a long time, baseline variation caused by IR source temperature drift and fluctuation, tilt of moving mirror, performance parameter change of beam splitter and lateral shift of detector were studied by simulating using MATLAB. Simulation results show that spectral baseline drift is approximately linear. On this basis, a novel method named spectral baseline correction by piecewise dividing (SBCPD) is proposed to correct spectral baseline in the present work. By comparing peak height of simulated spectra, it was found that performance of SBCPD is better than that of common methods of polynomial fitting, airPLS (adaptive iteratively reweighted Penalized Least Squares). And the application in gas well-logging showed that prediction accuracy of SBCPD is also higher. Additionally, this method is reliable and of less calculation, and is suitable for engineering application.