The invention relates to a grinding wheel external circle run-out detection method based on a laser displacement sensor. The grinding wheel external circle run-out detection method comprises the detecting step of: firstly, installing the laser displacement sensor in front of the external circle surface of a detected grinding wheel, and connecting circuits of detection equipment; determining a signal sampling frequency and a sampling length of each measurement of the laser displacement sensor according to measurement conditions of the detected grinding wheel; setting the signal sampling frequency fk and the sampling length Ls of the laser displacement sensor through computer software; inputting the signal sampling frequency fk and the sampling length Ls into a controller of the laser displacement sensor; and detecting the external circle surface of the detected grinding wheel by using the laser displacement sensor during the rotation of the detected grinding wheel, sampling data and transmitting the data to a computer, and processing and analyzing the sampled data to obtain an external circle run-out value of the detected grinding wheel finally. The grinding wheel external circle run-out detection method based on the laser displacement sensor achieves the real-time and precise measurement of radial run-out of the external circle of the grinding wheel.