Industrial Computed Tomography （ICT） technology provides a non-contact solution for precision measurement of small module plastic gears， effectively addressing multiple challenges in their metrological processes. This study provided a data-processing method for plastic， small-modulus gear point clouds obtained from ICT measurements. In the data-preprocessing stage， the gear measurement model acquired through ICT scanning was converted into a gear measurement point cloud， while a design point cloud was generated from the gear CAD model. Subsequently， point-cloud registration was performed between the measured and designed point clouds， consisting of four steps： pre-registration， coarse registration of the hole point cloud， fine registration of the hole point cloud， and registration of the gear-tooth point cloud. A measurement point-cloud segmentation method guided by the design point cloud was then adopted. The article first employed the DBSCAN algorithm to segment the designed tooth-surface point cloud， after which the segmented design point cloud guided the segmentation of the measured tooth-surface point cloud. Pitch-deviation evaluation points were extracted through this procedure to enable a comprehensive pitch-deviation assessment. Experimental results demonstrate that compared with gear measuring center measurements， the proposed method achieves the difference with maximum absolute value of single pitch deviation of 2.8 μm for left and right tooth flanks， and the difference with maximum absolute value of total cumulative pitch deviation of -6.6 μm. The developed ICT-based data processing methodology for gear pitch deviation measurement establishes a methodological foundation for precision evaluation of complex CT-measured gears， while providing valuable references for ICT-based measurement of other intricate precision components.