With consideration of large-scale cascading trip-off fault of wind generating, an on-line cascading fault early-warning system for large-scale wind power base is developed. Through the research of fault characteristics for wind generating cascading trip-off, the key links for building up cascading fault on-line early-warning system for wind power base are determined, including improving wind generator model and modeling wind generating protection and reactive compensation device. Based on on-line dynamic security analysis system, the scheme and basic structure of cascading fault on-line early-warning system for wind power base are proposed, including on-line data integration and contingency set, searching strategy for cascading trip-off fault, severity evaluation method for cascading fault, and parallel computing method. The system has been put into practice, which proves the rationality and effectiveness of the proposed method.