Roundness is an important index for evaluating the manufacturing accuracy and interchangeability of tiny cylindrical parts. In order to address the inaccurate positioning of the part in the roundness measurement process, which leads to the existence of tilting errors in the measurement data, a segmentation-interception roundness measurement method is proposed, in which the cross-section circle of the part is segmented into eight, ten and twelve equal parts, and the surface of the part is scanned linearly with a profilometer after the equal parts are divided, and a series of coordinate data obtained by scanning is used to characterize the arc contour of each segment, and then the center part of each segment is reconstructed to obtain the radius and roundness of the measured part. The center part of each arc is intercepted to reconstruct the cross-sectional circular profile of the part, and the radius and roundness of the measured part are fitted to realize the high-precision roundness measurement of tiny cylindrical parts. Taking a needle with a diameter of 3 mm as an example for roundness measurement experiments, the measurement results of different segmentation-interception cases show that the radius and roundness of the needle obtained by ten equal interceptions of 75° arc fitting are 1.500 892 9 mm and 0.092 μm, respectively, with a deviation within ±0.1 μm. The uncertainty components affecting the measurement results were analyzed by the GUM method, and the integrated standard uncertainty affecting the radius of cylindrical parts was calculated to be 0.049 96 μm, which demonstrated the reliability and consistency of the proposed splitting-intercepting circularity measurement method.