Design for assembly (DFA) has proved its success in manufacturing to face the market challenge. But the assembly process parameters were rarely concerned in the design for assembly. Aimed at this problem, an algorithm for design for automated assembly of circular parts was proposed. This algorithm can help designer to select the optimal process parameters, such as dimension tolerance of mating parts, location precision of assembly device and so on, subject to budgetary constraints. Finally a case is employed to explain the optimal course.