Abstract: By introducing the Customer Patience Value into inventory decision study, the customer service level model based on customer demand not lost completely is estabilished. The impact of Customer Patience Value on inventory cost was also analyzed in the model. Different from traditional models, the new model considers customers' choice of stockout, reflect the actual purchasing behavior more realistically. The introduction of Customer Patience Value in the model reflects the time value of customer demand, put forward the new way for enterprises laying down right inventory decisions in time-based competition.