As a country mostly surrounded by water, Korea plans to build a massive offshore wind farm off the west coast by 2019. Due to the different seabed condition, wind turbine with jacket foundation is considered as a suitable choice for the intermediate water depths so far. And preliminary work is necessary for the wind turbine manufactures. In this work, a 3-blade upwind, pitch controlled, variable speed 5 MW offshore baseline model is used. Two different jacket foundations are designed for the water depth of 30 m. Using several load cases, the dynamic response of two kinds of jacket structures, are compared by modal analysis and dynamic analysis. The analysis results of the system natural frequencies, significant loads of different jacket members for both models are given in detail. This research gives a good knowledge of large scale offshore wind turbine in Korea for intermediate water depth. (C) 2012 Elsevier Ltd. All rights reserved.