In order to improve the level of customer service in container terminals, this study suggests the operation of buffer yard which is located between a gate and marshalling yard Also, the interface between outside trucks and unmannd container handling equipment can be easier through buffer yard Supposing all the arrivals of outside bucks is known in advance, the container handling process at buffer yard are described in terms of a delivery and receiving operation. The simulation model is suggested to evaluate the performance of buffer yard. Experimental results are provided to analyze delay time of outside trucks under various circumstance.