OBJECTIVE： To provide reference for drug procurement and inventory control in hospital pharmacy. METHODS： Referring to the new definition of DDDs in clinical application amount and inventory control amount， the application of DDDs in the formulation of drug purchase plan and stock control was introduced to validate the rationality of its application based on the practice of the hospital. RESULTS & CONCLUSIONS： DDDs represent drug dosage or inventory dosage within a certain time range. According to this definition， DDDs can be used to predict the amount of some drug or some type in the future； purchase pr- inciple of “frequent purchase”is not reasonable due to workload increase； reasonable inventory amount could be confirmed， so that inventory amount can be reduced as much as possible under the guarantee of drug type supply. Through the practice of 2 long holidays in our hospital， drug purchase plan on the basis of new definition of DDDs not only guaranteed drug supply but also reduced inventory amount； not only simplified and accuratelied formulated purchase plan， but also reduced workload of inventory control.