Abstract: Aiming at the problems of few measurement points and low measurement efficiency in the measurement of steel rulers by image method, a dynamic measurement method using a laser displacement sensor as the scale line aiming device was studied, and a dynamic measurement device for steel rulers was established. The device consists of a laser displacement sensor, a standard length generator, a signal processing system, etc. A high-precision synchronous belt drive linear module is used to control the horizontal displacement of the laser displacement sensor. A high-precision grating ruler is used as the standard length generator. When the laser displacement sensor beam scans the scale lines of the steel ruler, the signal processing system outputs sampling pulses, and the computer synchronously collects grating displacement data. The measurement results are output through the self-developed visualization measurement and data processing software. Experimental verification shows that the device realizes the dynamic automatic measurement of the full scale lines of steel rulers in the range of (0～1000) mm. It only takes (5～8) min to measure 2000 scale lines, with a standard deviation of about 4 μm for the measurement repeatability in the 1000 mm range.