The condition monitoring system is essential for a large-scale wind turbine system to maximize its availability and reliability. In order to develop its effective condition monitoring algorithms, a wind turbine simulator is necessary for such a large-scale system. However, the existing simulators consisting of a motor and a generator are not suitable for this purpose, because they have not the general configuration of wind turbine systems. To solve this problem, we are now developing a novel wind turbine simulator that is composed of blades, a step-up gearbox and a generator. This paper presents a developed condition monitoring system and the design procedure of the wind turbine simulator.