When a regional power grid with a high proportion of small hydropower and new energy operates in a passive isolated grid, the inner stability characteristics of the isolated grids is directly affected by the small hydropower governor parameters and new energy control protection configuration. Based on the typical cases of the actual isolated grids, the dominant factors affecting the frequency stability of each stage of the isolated grids are analyzed, and a typical example simulation model adapted to multi-type isolated grids is constructed. Through multi-dimensional quantitative simulation comparison analysis, the general principles of coordination of small hydropower to grid and optimization of new energy grid-related parameters in the operation of regional isolated grids are proposed. The research results support the development of safety and stability control plans for isolated grid operation, and assist in the construction of new power systems and the reliable power supply of regional power grids.