Abstract: Since the NPP real-time information monitor system is at the stage of development, and the related standards and regulations are not built completely now, network security and data security are key fields in the monitor system design. The factors affecting network and data securities of monitor system were analyzed, and several precautions and solutions were proposed. The effective technical methods such as safety isolation, redundancy design, data backup and data buffer were applied to ensure the data unilaterally transfer, system continuously work and data integrality. Taking the monitor system of some 2×1 000 MW nuclear power units for instance, the network configuration and the implementation of network and data securities were introduced, which provides reference for the engineering technical personnel.