The invention provides a rain system for testing a vehicle roof high-voltage system of a railway vehicle. The rain system comprises a control system, a supply and drainage system, a spraying system and a water collection system, wherein an output end of the supply and drainage system is connected with an input end of the spraying system to provide a water source for simulating rainfall of the spraying system; the output end of the spraying system is connected with an input end of the water collection system, the water after simulating the rainfall is collected by the water collection system, the other input end of the water collection system and the supply and drainage system are connected with each other, the water collected by the water collection system is input to the supply and drainage system, the water discharged after the end of the work of the supply and drainage system is supplied to the water collection system, an output end of the control system is connected with the supplyand drainage system so as to control the flow rate and pressure of the supplied water, and the other output end of the control system is connected with the spraying system to achieve real simulationof a rainfall environment. The rain system provided by the invention realizes the simulation of light rain, moderate rain and heavy rain in an insulation performance test of the vehicle roof high-voltage system of the railway vehicle, the pressure, the rainfall and the direction can be adjusted by the control system, the structure is simple, the operation is convenient and intuitive, the reliability is high, the test time is shortened, and the test efficiency is improved.