The decomposition of annual runoff total control index is the key link to the implementation of low impact development. The rationality and maneuverability of the decomposition index are not only the key point but also the difficulty in the planning and design of sponge city. Combining the two commonly used decomposition methods,"volume method" and "model calculation method", a "double guiding method" is proposed. By optimizing the index adjustment system, the application research of the index decomposition is carried out to improve the guidance and feasibility of the decomposition index value...