The present invention belongs to the field of power plant equipment life assessment and safety and particularly relates to a power plant steam and water system comprehensive corrosion monitoring system and method. The monitoring system is formed by a power plant steam and water system comprehensive corrosion management platform, a management personnel function module, a basic information function module, a working medium corrosion product monitoring module, a water chemical treatment module, and a corrosion expert function module. According to the system and the method, the corrosion data management of the aspects of a steam and water system pipeline metal side and a working medium side is provided, with power plant steam and water system state monitoring and life management as an overall target, a technical evaluation and analysis system is complete, all corrosion information of a power plant steam and water system is shared, the information exchange amount is improved, and a theoretical basis is provided to ensure the safe and reliable operation of the power plant steam and water system.