Non-uniform scroll parts are more difficult to be examed with traditional fixtures and calibration precision is relatively low because of their compicated shape. In response to the above feature, an approach of rapid precision diagnosis of non-uniform scroll part based on reverse engineering is presented. First a 3D solid model of non-uniform scroll part was created in the Pro/E environment and used as the reference model, and then cloud data of the scroll part machined was collected using the ROMER measuring arm and treated as digital model. The two models are compared to abtain machining precision information of the scroll part. Graphics-directed matching principle of mathematical models is proposed to improve alignment precision of the digital model. In this approach, alignment of multi-look cloud data, de-noising of scattered cloud data and data compacting integrated by random and curvature sampling are adopted to decrease the data-processing error. Analysis of 2D, 3D and geometric tolerance evaluation between the reference and digital models show that the machining precision and geometric tolerance of the presented non-uniform scroll part are satisfied. This study provides a rapid, accurate and visual method of precision diagnosis for complex surfaced mechanical products.