Aiming at the wide application of technological design in three-dimensional CAD software, while the technological dimension chain’s calculation is completed in the two-dimensional process sketch still. A sort of method of calculating technological dimension chain was put forward, which is based on three-dimensional process model. Three-dimensional process model is created through the process of technological design by introducing the concept of three-dimensional process model, and then, the information of process dimension is extracted from the three-dimensional process model and a tree oriented process dimension structure is established. On the basis of the above, we can proceed with technological dimension chain’s integrated calculation and analysis, redistributing the process dimension and its corresponding allowance dimension and tolerance. It will offer more reasonable and reliable process parameters to the technologists in the design of process route, and also effectively solve the problems of the technological dimension chain’s calculation involving to CAPP system in the environment of three-dimensional CAD software.