The invention discloses a drawing and coding method for large-scale complex river network massive fine regular grids of a river basin. The method comprises the steps of S1, identifying structure layers and boundary range layers of a river basin water system body; S2, obtaining river reaches of rivers of a river basin water system segment by segment; S3, drawing two-dimensional regular grids of the rivers and coding the grids in the rivers; S4, carrying out two-dimensional compilation on the two-dimensional regular grids, thereby obtaining an integrated grid; S5, carrying out one-dimensional compilation on the integrated regular grid; and S6, establishing one-dimensional grid relationships. According to the method, on the basis of an existing massive regular grid method and tool, the large-scale massive grids are increased, reduced and coarsened simply and effectively, the grids are drawn once and can be used for life, and the data support is provided for calculation of values based on the regular grids.