At present, with the continuous consumption of primary energy, oil shale has come into people′s sight with its rich reserves. At the same time, the use of primary energy has aggravated the emission of CO2, resulting in different degrees of environmental problems, and researches have shown that CO2 can be used to produce gas. Therefore, in order to explore the effect of CO2 atmosphere on oil shale pyrolysis, thermogravimetric infrared spectroscopy (TGA-FTIR) was used in this paper to explore the pyrolysis weight loss of oil shale under five different mixing atmospheres (CO2 and N2 mixed in different proportions) and different heating rates. Solid-phase Fourier infrared spectrometer was used to detect the solid-phase products. Peakfit software was used to perform peak fitting analysis of gas/solid phase Fourier infrared spectra. The results show that the total weight loss rate of oil shale pyrolysis shows a weak trend of first increasing and then decreasing with the increase of CO2 concentration, which makes the peak of weight loss rate move to the high temperature region, and increases the weight loss rate of oil shale pyrolysis in the third stage. Excessive CO2 inhibits the pyrolysis of oil shale. With the increase of heating rate, the total weight loss rate of oil shale pyrolysis decreases. Under the same conditions, moderate CO2 concentration increases the production of CnHm and CH4, while excessive CO2 inhibits their production. For semi-coke, the vibration intensity of carbonates in CO2 atmosphere decreases, and the pyrolysis temperature of some functional groups changes. Under the same pyrolysis conditions, there are more kinds of functional groups and higher intensity in the char under CO2 atmosphere, and the pyrolysis reaction moves to the high temperature region.