This Paper discusses how to estimate the container yard space of a port container terminal as well as how much the Inventory level of containers Is affected by related factors such as allowable dwell time for containers, handling volume per containership, and loading/unloading productivity of a port container terminal. Under the assumption of static relations among the factors, a model for estimating the container yard space is suggested. In terms of arrival patterns of containers, sub-models for export, import, and transshipment containers are constructed separately. A numerical example and the sensitivity analysis for some parameters are provided to help intuitive understanding the characteristics of the suggested model. The experimental results show that the allowable dwell time for containers is the most critical one of the factors to influence on the maximum Inventory level of containers.