The invention relates to a method and system for extracting information of an urban water body. The method comprises: S1, carrying out data preprocessing on an urban remote sensing image captured by a satellite to obtain a preprocessed image; S2, carrying out image segmentation on the preprocessed image according to a preset segmentation parameter to obtain a mean value image having feature groups including a spectral feature, a topological feature, a shape feature and an length-width ratio feature; S3, carrying out a spectral feature analysis on the mean value image to obtain a typical ground object spectral curve graph including spectral curves of all typical ground objects containing a building, a water body and a shadow, at all wave bands; and S4, according to the feature group, extracting water body information in the typical ground object spectral curve graph. According to the invention, the method and system have the following beneficial effects: the water body is effectively extracted based on the spectral features of the ground objects, the shape features, topological relations, and length-width ratio information of the ground objects; and the extraction accuracy is ensured.