The invention discloses a network intrusion alarm method based on a nuclear power plant. The method comprises the steps that data information sent by a visit object is detected, wherein the detection comprises misuse detection and protocol anomaly data detection; if the detection result of the data information is abnormal, real-time early warning information is generated; the real-time early warning information and historical early warning information in a database are matched; and if the matching result of the real-time early warning information and the historical early warning information does not accord with a preset matching value, intrusion alarm information is issued. The network intrusion alarm method based on the nuclear power plant, which is provided by the invention, can effectively meet the requirement of network security protection of an industrial network of the nuclear power plant. In addition, the invention further discloses a network intrusion alarm system based on the nuclear power station.