The invention provides a rolling mill equipment state online monitoring and diagnosis system and monitoring and diagnosis method. The rolling mill equipment state online monitoring and diagnosis system comprises a data analysis module, a servo valve difference value analysis module, an electric sensor oscillation analysis module, a rotary part vibration signal analysis module, an information comprehensive processing module, a fault alarming module, a monitoring view module, a channel management module, a standard management module and a fault feedback module. A large amount of encrypted production data files in the system are analyzed, so that the data storage space is greatly saved, and the fault data tracing and the big data-based deep analysis are facilitated; through extraction and analysis of different signal features of a servo valve, an electric sensor and a key rotary part, a rolling mill equipment state can be monitored and diagnosed online multi-dimensionally; and through therolling mill equipment state online monitoring and diagnosis system, the rolling stability and the product quality index control precision are improved.