The power coefficient of reactivity (PCR) needs to be negative to achieve the inherent safety of a reactor, but the PCR of CANDU-6 has been evaluated to be positive in recent studies. In this circumstances, an experiment was performed at a CANDU-6 reactor in Korea to measure the PCR of CANDU-6. Based on the measurement data, the PCR was evaluated by a newly proposed methodology which requires several estimations of reactivity variation due to liquid zone controllers, xenon, etc. Consequently, the PCR of CANDU-6 was evaluated to be about 0.5 pcm/%Power which is slightly smaller than the latest official value, 1.7 pcm/%Power.