The invention provides an elongated shaftless spiral sand-water separator used for preventing sands from sliding down and having a very large installation inclination. The bottom of the sand-water separator is immersed in deepwater, and can bring out sands without water from the deepwater, because the upper portion of the sand-water separator is an opened U-shaped sand conveying tank. Sands simultaneously enter every position of the tank, so the sand-water separator has large throughout, is difficult to obstruct and is convenient to maintain. The sand-water separator comprises a hollow helix 1, the U-shaped sand conveying tank 2, a deceleration motor 3, a spiral blade connecting mechanism 4, a discharging opening, and a shaft coupling.