Abstract: The work described is intended to develop an interactive computer aided dimensional planning system that can be used to perform efficiently the calculation for dimensional planning, to adjust economically and reasonably the working tolerances for each machining operation in any program of process planning. To this end, a mathematical model, incorporating a Matrix-Tree-Chain method, of a tolerance chart and the method of tracing has been established based on the tolerance chart technique. It makes possible the calculation and adjustment of working tolerances in the process of dimensional planning on a computer.A mathematical method for specification and adjustment of tolerances in manufacturing processes is proposed.The interactive computer aided dimensional planning system （CADP） is presented, which can work independently or be integrated with a CA-PP （Computer Aided Process Planning） system.