Gear tooth profile deviation is one of the important parameters in gear verification. A new type of composite gear line structured light measurement system is used to measure the tooth profile of the first-level standard (u=1μm, k=3) gear involute template, and analyzes from the mechanical, thermal, optical, and electrical aspects. The source of measurement error, and based on JJF1059.1-2012 "Measuring Uncertainty Evaluation and Guidelines", evaluated the uncertainty of measuring gear tooth profile deviation with this system. Research shows that there are errors when using this measuring system to measure gear tooth profile, including: instrument measurement repeatability error, involute model standard error, model linear expansion error, center coaxiality error, gear installation eccentricity error, line structure Optical system error, etc. The combined standard uncertainty caused by CCD camera calibration error, structured light vision model calibration error and line structured light strip center detection error is 0.98μm, which is the main error of the new composite gear line structured light measurement system Source, and through analysis and calculation, the extended uncertainty of the measurement system is 2.3μm(k=2), which can meet the gear measurement with a measurement accuracy of 2.3μm or more.