Abstract: In car renting,customer demands rental time are subject to random variation.Thus,it is difficult to model and optimize such a process.The car renting is treated as a realtime queuing process.Based on this concept,for a car rental company,aiming at maximizing its profit by determining the number of vehicles needed,a mathematical model is developed.With this model,the profit obtained by two companies under cooperation is compared with that obtained without cooperation.Results show that more profit can be obtained with cooperation than without cooperation.Furthermore,based on the total profit increase for the two cooperative companies,the acceptable sublet price range is presented.Thus,by using the proposed method,a car renting company can select its most profitable operation policy.Numerical examples are given to verify the proposed method.