This paper dirvers two formulas to calcualte the average inventory yielded by fixed interval withdrawal Kanban and supplier Kanban, respectively, in Toyota Produciton System. Secondly, two formulas to determine the minimum number of Kanbans to be required for fixed interval withdraewal and supplier Kanban are shown. An algorithm to obtain the optimal order cycle is proposed to minimize the total operating costs composed of the inventory costs and te order costs by Kanban System.