In order to determine the reasonable number of midtown berths to not only satisfy the need of basic trips but also be able to restrain excessive trips causing network congestions,an analysis was first made of the trip behavior of drivers under a restricted supply of parking berths,and different attributes of drivers were defined to characterize the trip desirability and decision behavior of different drivers.Then,a model for optimizing the number of parking berths was constructed to satisfy the maximum parking demand and to maximize berth utilization within the maximum capacity of road network.The solution of the model was introduced.A numerical example shows that with the model the optimal number of parking berths of the midtown can be determined,which can provide scientific bases for parking demand management.