The invention provides a tank washing device and system. The device comprises a first water pump, a sloping plate settler, a water storage tank, a second water pump and a cleaning nozzle. The first water pump is connected with the bottom of a tank body to be cleaned for conveying liquid in the tank body to be cleaned to the sloping plate settler. The sloping plate settler is connected with the water storage tank and used for conveying liquid obtained after settling treatment of the sloping plate settler to the water storage tank, and the second water pump is connected with the bottom of the water storage tank and connected with the cleaning nozzle arranged in the tank body to be cleaned for conveying liquid in the water storage tank to the cleaning nozzle to be sprayed out to clean the tank body to be cleaned. Due to cooperation of the first water pump, the sloping plate settler, the water storage tank, the second water pump and the cleaning nozzle, recycling water in the tank washingprocess is rapidly settled and filtered. Accordingly, by adopting the component device of the small size, large-cleaning-amount or rapid cleaning operation is performed, the settling and filtering effect is good, the cleaning quality is improved, and the service life of conveying equipment is prolonged.