Abstract: The diagnosis should be conducted before the nuclear power station enters into emergency operation procedure, and the diagnosis procedure will lead the operators to implement the emergency operation procedure. At present, all the domestic in-service nuclear power stations adopt the manual diagnosis, but for the 3rd generation units CEPR in Taishan nuclear power plant adopts the latest technique – the automatic diagnosis strategy. In this paper, a simple comparison of the two methods adopted for accident treatment in nuclear power stations is included, and the detail presentation about the logical flow of automatic diagnosis is emphasized. Besides, the feasibility and superiority of automatic diagnosis adopted in the nuclear power station is analyzed.