The invention discloses an in-situ automatic collection device for a sand-laden water body of shallow water. The device comprises a triangular bracket, an angle controller, a water inlet control panel, a fixed rod and a control system, wherein the lower end of the fixed rod is connected with a tubular water sampler through a rotary fixed seat; the water sampler is provided with four attitude control wings, and a motor and a flow baffle are arranged in the water sampler; the water sampler is connected with a bleeder hole in the water inlet control panel through a communicating pipe arranged in the fixed rod; a through hole is formed in the middle of the water inlet control panel; an irrotational fixed hole is formed in the lower half part of the through hole; and a rotatable fixed hole is formed in the upper half part of the through hole; and a vacuum flask fixing tray is arranged at the upper part of the water inlet control panel through a rotating shaft in the rotatable fixed hole. The in-situ automatic collection device is simple in structure and convenient to operate, the water collection direction can be controlled, sampling along the ocean current direction is achieved, the in-situ automatic collection device is suitable for in-situ automatic collection of the sand-laden water body of the shallow water, and the in-situ automatic collection device and method have the advantages of being accurate in sampling depth, convenient, fast and high in automatic degree in comparison with traditional water sample collection device and method.