Abstract: Currently, most NPP operators have attached great importance to the optimization of outage duration. By taking various optimization measures, the operators have managed to optimize the outage duration and improve the operational performance. CANDU NPP, with its unique feature of on-power refueling and less constraint from fuel burn-up, offers the opportunity of longer outage cycle. With the extension of outage cycle, it is possible to reduce the number of outages in the life time of NPP, minimize the number of shutdown and start-ups, increase the outage preparation lead-time, and improve the manpower preparation and training for outage, which could effectively lead to improved capacity factor, outage and operational performance in the life time of the NPP. This paper provided the preliminary study results and process for outage cycle extension taking into account the situation of CANDU NPP in China and abroad, aiming to further improve the operational performance and competitiveness of CANDU NPP in China.