Tolerance specification is the activity of specifying tolerances. In current 3D-CAD system, tolerance types and tolerance values are specified by designer manully, and the validity checking of tolerance is no available. To achieve semi-automatic tolerance specification, geometric feature in the next-generation Geometrical Product Specifications and Verification (GPS) was introduced, the corresponding rules between geometric features and tolerance types were presented; The recommended values for tolerance were stored in a database system and constrainted by tolerance principles. Additionally, the implementation of computer aided geometric tolerance specification was proposed. Finally, the initial prototype system was developed to demonstrate the proposed scheme, which aides designer to define reasonable tolerance types and tolerance values in 3D-CAD system.