The invention discloses a mid-infrared laser measurement system and method for engine combustion process monitoring. The measurement system comprises a laser device and detectors, the laser device cantransmit mid-infrared laser within a specific wavelength range, and the mid-infrared laser is absorbed by engine combustion flames. Particularly, the laser transmitted by the laser device is dividedinto two beams by a beam splitter, one beam of laser passes a laser calibration device and is measured by the first detector and used for calibrating wavelengths generated by the laser device, the other beam of laser is absorbed by carbon dioxide gas generated by combustion, measured by the second detector and acquired by a data acquisition system, and concentration information of carbon dioxide can be acquired by processing, so that the combustion efficiency of an engine is acquired. According to the system, background absorption interference of the carbon dioxide in an environment is omittedwithin the selected laser wavelength range, the carbon dioxide is obviously absorbed in the high-temperature environment, interference of other combustion products such as water molecules and intermediates is omitted, and high measurement accuracy of the combustion efficiency of the engine can be achieved.