Provided is an automated periodic surveillance testing method and apparatus in a digital reactor protection system, which unites a passive testing means such as a self-diagnosis or an on-line state comparison with an active testing means such as an automatic logic test and the like in the digital reactor protection system. Accordingly, a device self-diagnosis, an on-line state diagnosis, and an automatic logic test are used as the automated periodic surveillance testing method in the digital reactor protection system. Thus, the time consumed in a periodic surveillance test can be minimized, thereby saving reactor operating costs, and excessive manpower can be avoided, thereby decreasing potential human errors. Also, a channel detour time at which one of multiple channels is detoured can be minimized based on the automated periodic surveillance test in the digital reactor protection system, thereby enhancing stability.