Abstract: A similarity (or health condition evaluation) curve-based equipment fault early detection and operation optimization methodology and system, includes: selection of normal operating data from historical equipment operation records; generation of data collection from normal operating data, and creation of a data model covering equipment multi-operation conditions based on the distribution of data collections; creation of a health condition evaluation or condition similarity curve using continuous relativity calculations between online real-time operating data and historical data in the model; automatic generation of equipment health condition safety baseline through scoring on historical normal equipment operation records; Based on the change of equipment health condition evaluation curve against the safety baseline, in combining with identifying abnormally-changed process variables which lead to the decrease of health condition evaluation values, early warning on equipment health condition change is published