The analyses of state of art trends of developing CAD systems for mechanical engineering products and methods of computer aided workholders design are offered. The framework of the environment model to support the optimal workholder design (DESIGN SPACE) is described. Technique to represent information and knowledge for family of similar products is offered. This approach is based on the tree graph structures to model the designed products and used components. For specify the DS the two types of structuring techniques are adopted: AND decomposition for concurrency, and OR decomposition for clustering of optional solutions. The case base reasoning approach (CBR) for the solution of problems is applied and described. The fact is that many of workholder designs are not very different from what were done in the past. There are obvious benefits in cost and time saved if the best practices are captured and made available to use. The proposed new approach has been tested at the example of development of the integrated design environment for modular workholder design at TUT, Estonia.