In order to accurately obtain flaw depth parameters of a gun barrel, a new flaw depth measurement method based on the equivalent multi-baseline stereo imaging is proposed, and an automatic measurement system for the flaw depth is established in this paper. The Tsai two-step method is used to calibrate the camera,and the equivalent multi-baseline stereo imaging methods are taken to obtain the flaw image. On the basis of the above, this system extracts the image features and realizes the stereo matching processing according to the calibration data and location parameters. Then, it obtains the precise flow depth value and implements the accurate measurement of flaw depth parameters of the gun barrel. The test results show that the measuring absolute error of this flaw depth measuring system is less than 0.1 mm, and the relative error is less than 5%.These results can meet the need of the gun barrel for flaw depth measurment,and can provide an important technical support for the identification testing.