Abstract: The repair process,factors affecting batch size and its determination method are analyzed.Basing on the queue theory,a universal model of calculating the support equipment quantity under the condition of different sending policy is proposed and which is different from the routine method which is established on the base of one by one replenishing.Through the model the first difference and second difference of the number of support equipment and the batch size are analyzed and which are all have influence on the waiting time.In the end,the model is also used in a numerical study.