Abstract: An agitator includes a trough having a first end, a second end, a top, a bottom, an inlet on the top and close to the second end, and an outlet on the bottom and close to the first end, an axle rotatably mounted between the first and second ends of the trough and enclosed with an inner spiral vane, the inner spiral vane being fixedly mounted on the axle and gradually decreased in outer diameter, the inner spiral vane being provided with an edge close to the first end of the trough, and an outer spiral vane enclosing the inner spiral vane and fixedly mounted on the inner spiral vane, the outer spiral vane being opposite to the inner spiral vane in spiral direction, whereby the agitator can be stir a mixture thoroughly and rapidly.