A visual measurement benchmark algorithm for thread crest line regression, correction, and evaluation is proposed to address the challenges of rapid benchmark positioning for small thread and large-diameter measurement in industry applications. Gaussian filtering is used to eliminate image noise, and the edge transition zone of the thread image is extracted based on a dual threshold binary method. An image coordinate system is then established. Feature points are extracted to preliminarily determine the thread center axis, which is used as the measurement reference. An image rotation regression model is constructed to perform the first correction of the thread measurement benchmark. Using the left thread crest line as the measurement benchmark, a statistical measure of the goodness of fit of a quantitative regression model with a coefficient of determination is used to adjust the measurement benchmark for the second time. Finally, the corrected coefficient of determination is used to evaluate the positioning accuracy of the measurement benchmark. On this basis, a major-diameter measurement algorithm is proposed by statistically analyzing edge transition information in thread crest images. The expected edge of the thread crest is projected onto the x-axis, and large-sample statistical data are used to determine the thread crest-edge position. The thread diameter is then calculated at the expected positions of the left and right thread crests, and the algorithm is calibrated using standard gauge blocks. The algorithm and measurement accuracy were experimentally verified through high-precision edge measurement of measuring blocks. The experimental results show that when the center axis of the equivalent block has a certain inclination angle with the x-axis, the maximum deviation obtained using the proposed algorithm is 0.001 7mm. Measurement experiments were conducted on the same metric thread, M2.5, using the MV-TOSEDP high-precision automatic image measuring instrument and the 103341 thread measuring machine, respectively. When the central axis of the thread has a certain inclination angle with the x-axis, the difference between the two test results is 3.1 μm, and the maximum measurement deviation is 8.8 μm. The average measurement time of the proposed algorithm is 2.480 1 seconds. In summary, the regression correction measurement method for the thread crest line satisfies the fast measurement requirements of metric small threads based on the visual measurement of the large diameter benchmark.