The article deals with the principles of fixtures design and their application at virtual modelling in CAD/CAM system. The computers have became an important part of our life and about its benefits nobody doubts. The designers have got the strong tools into the development hands that use the potential of computer techniques for the creation of completely new applications, which alleviate the solution not only of common problems, but already the special defined, too. New technologies bring the change of mind. The classic way “production on the base of drawing” is often substituted by computer aid technology that thanks to three dimensional graphic enables to solve the difficult phases of the body design direct in its real version of full-value stereometric body. In the article are described the principles of the fixtures design using CAD/CAM system following by application of these rules for machining of complex shape armature.