The invention belongs to the technical field of geotechnical engineering, and relates to a sand-rain-method sand shakeout device capable of automatic sand supplementing and flow rate controllability. The device includes a portal frame, a hoisting and translating gear, a sand hopper, sieve screens, a control panel, a baffle plate and a PLC controller. The inside of the sand hopper is divided into an upper layer and a lower layer, and the bottoms of the upper and lower layers are provided with the sieve screens. The control panel is adsorbed on the sieve screen at the bottom of the lower layer of the sand hopper. The flow rate of sand is controlled by changing the shape, the size and the position of the control panel. The baffle plate is inserted horizontally into a slot at the bottom of the sand hopper, and controls the bottom of the sand hopper to be opened and closed. The PLC controller is connected to the hoisting and translating gear, and controls hoisting and translating movements of the hoisting and translating gear. The device has characteristics of a simple structure, convenient operation, a low investment cost, a high one-time load, and capability of automatically controlling two-dimension movements, supplementing sand and effectively saving human labor. Uniformity and repeatability of samples prepared by the device are good and can meet requirements of most tests.