The performance of a power plant is highly dependent on the performance of its control loops. So real-time performance monitoring to identify poorly or under-performing control loops has become an integral part of preventative maintenance of power plant. Korea Electric Power Corporation (KEPCO) has developing control loop performance monitoring (CLPM) system which can interface with several DCS to have original technology. This paper introduces general CLPM technology and commercial solutions. And then describes basic functions of the CLPM which has been designed to monitor automatically and continuously the performance of control loops of power plant.