Based on spectra measured by the open-path Fourier transform infrared (OP-FTIR) spectroscopy technology, the two-dimensional concentration distribution of the gas in a Gaussian spatial distribution model was reconstructed using the algebraic reconstruction technique (ART) and the maximum-likelihood expectation-maximization (MLEM) algorithms. Two evaluation indexes, the nearness and the correlation coefficient, were used to analyze the reconstructive accuracy and anti-noise performance of the reconstruction algorithms. In the single-peak concentration field of the gas, the nearness of the ART and MLEM results were 0.177 and 0.044, respectively, while they were 0.263 and 0.069, respectively, in the double-peak concentration field. The results therefore indicate that MLEM is more suitable for complex concentration distributions. Conversely, at different noise levels, the anti-noise performance of ART is better than that of MLEM, which is more sensitive to noise.