The invention relates to a hydraulic model with the International Patent Classification (IPC) No. of E02B 1/02, in particular to a river space-time self-moulding model which simulates a downstream alluvial plain of an alluvial river and includes the natural formation and development process of a river. The model comprises a model water tank, a large stirring pool and a small stirring pool, wherein the small stirring pool is communicated with the large stirring pool by a pump; the large stirring pool is communicated with an opening box; the opening box is communicated with the model water tank; the model water tank sequentially comprises a model inlet section, an alluvial river self-moulding precipitation area, a flow field monitoring system, a water level probe, an overflow weir and a water return pool in which the water flows by the overflow weir; and the water return pool is communicated with the small stirring pool by a water return channel. The invention establishes the river space-time self-moulding model by synthesizing the advantages of a river natural model and a microscale model and can automatically simulate the space-time natural evolution process of the river, researchthe influence mechanism of the water and sand process on the river shape and the river potential change and research the feasibility of river comprehensive regulation measure and technology.