The invention relates to a side slope testing device for simulating rainfall space time changes. The side slope testing device for simulating rainfall space time changes comprises a rainfall simulating unit, a test platform unit and a data acquisition analyzing unit. The rainfall simulating unit comprises a rainfall loop formed by a water tank, a water pressure pressurizing part, a plurality of electromagnetic valves and a plurality of nozzles which communicate through a water pipe. The water pressure pressurizing part is arranged on a pipeline of the rainfall loop, and the data acquisition analyzing unit separately controls the closing magnitude of the electromagnetic valves to control the drainage flow strength on different pipelines, so that time and space distribution of rainfall is simulated. The side slope testing device for simulating rainfall space time changes, provided by the invention, is simple to operate and has the characteristics of high automatic degree of data acquisition and high repeatability.