Abstract: To address the challenge of measuring the axis of large-diameter holes in the aerospace manufacturing field, we propose a hole-axis measurement method based on photoelectric detection technology and collimated lasers. Firstly, the probe is stably supported inside the hole to be measured, using the collimated beam emitted by the single-mode fiber laser as the measurement reference. The PSD sensor at the front end of the probe measures the coordinates of the collimated laser spot to determine the relative position of the probe, while the inclination sensor data corrects the clamping posture error. Then, the laser distance measuring sensor rotates under the motor drive and measures the distance to the hole contour points. Combined with the data from the internal angle encoder of the motor, the center coordinates of the measured hole on the current section are calculated. By moving the probe and measuring multiple sections in succession, the axis of the measured hole is determined based on the centers of all sections.Experimental results show that the repeatability error of axis measurement of this system is less than 0. 01 mm, meeting the requirements for measuring the axis of general large-diameter holes.