A model of side pattern CAD/CAM on mould for auto lamp integrated with CATIA V5 is built. After analyzing the properties of design and the manufacture of side pattern on mould for auto lamp, key technology, such as grouping, sorting, determination of continuity, fairing and fitting of side pattern curves, generating of NC files and G codes, are presented. Using out-process redeveloping tools of CATIA V5, a CATIA V5 integrated side pattern CAD/CAM system for mould of auto lamp is developed. At last, a practical example shows that the technology and the software satisfy the design and manufacture of side pattern on mould for auto lamp. The technology and the software have been used in related enterprise successfully.