The invention provides an absorption spectrometer. The absorption spectrometer comprises a spectrometer host, a sample cell and a heating furnace, wherein the spectrometer host provides a light source and a detector; the heating furnace is provided with an optical view window allowing light rays to pass through; the sample cell comprises a sample cell main body for accommodating a to-be-detected sample, and the main body is of an inverted 'T' shape, and comprises an optical channel extending horizontally and an auxiliary channel extending perpendicular to the optical channel; two sides of the optical channel are sealed by window sheets; and the tail end of the auxiliary channel is provided with a ventilation plug, wherein the window sheets of the sample cell, the optical view window of the heating furnace and the center of light bundle sent out by the light source are consistent. The spectrometer not only can determine the absorption light spectrum of a sample with the corrosivity at the temperature as high as 500 DEG C by the additional arrangement of the heating furnace and the improvement of the sample cell, but also has the advantages of good safety, high operability, wide application range and the like.