A cyclical and continuous device and method for wet sieving of polysaccharide granules are provided. The device includes a first dosing tank, a second dosing tank connected to the first dosing tank by a first circulation pump, a first suction filtration tank connected to the second dosing tank by a second circulation pump, and a second suction filtration tank connected to the first dosing tank by a third circulation pump. An overflow port provided on a side wall of the second dosing tank is higher than a feed port of the first dosing tank. A sieve of a mesh filter for coarse powder is disposed in the first dosing tank. A sieve of a mesh filter for fine powder is disposed in the second dosing tank. A stirring device is disposed in both the first dosing tank and the second dosing tank.