The invention designs a laser light ray deflection correction device and method based on a modulation sawtooth wave signal. The device comprises a visible light laser light source, an infrared tunablelaser light source, an optical fiber coupler, a collimator, a dichroic beam splitter and a photoelectric detector and the like. The method comprises the following steps: to begin with, controlling the visible light laser light source and the infrared tunable laser light source to emit calibration light and detection light in the form of same-amplitude and same-phase wawtooth wave scanning signalsobtained after high-frequency sine wave modulation, wherein the two paths of light have light-intensity fluctuation due to influence of the ray deflection effect after passing through a measured temperature area, the light-intensity fluctuation being reflected in the amplitude variation of sine waves; extracting amplitude variation of sine wave signals of the calibration light to obtain light-intensity fluctuation caused by the ray deflection effect; and carrying out correction on the light intensity signal of the detection light by utilizing the amplitude variation of the sine waves of the calibration light, and only keeping corresponding laser absorption information, thereby realizing correction of the ray deflection effect. The method has an important use value and broad application prospect in application of a laser absorption spectrum wavelength modulation method.