Abstract: The internal cavities of components with large length-to-diameter ratios, such as landing gear struts and gun barrels, commonly feature geometric characteristics like multi-stage stepped holes with variable diameters. To address the issue of low measurement accuracy in existing methods, which arises from difficulties in compensating for axis eccentricity and mechanical eccentricity, an adaptive bore diameter calibration method is proposed. Firstly, the sources of measurement errors were analyzed. Secondly, an eccentricity error compensation algorithm for measuring different diameters was investigated, and a precision integrated measurement scheme along with the adaptive bore diameter calibration method was proposed. Finally, an integrated automatic measurement device for multiple diameters in the deep-hole reverse cavity of landing gear struts was developed. Experimental results demonstrate that for diameter measurements within the range of ϕ135−175 mm, the mean absolute error is reduced to 0.017−0.020 mm after applying the adaptive calibration method, which represents a reduction of 57.5%−66.4% compared to the error before calibration. Precise measurement of multi-stage variable-diameter stepped holes in the deep-hole reverse cavity of landing gear struts is achieved, providing strong technical support for the precision manufacturing and accuracy control of landing gear.