The present disclosure relates to an integrated collet and a downhole plugging system, and a plugging method thereof. The integrated collet includes a collet body, wherein the collet body can form a seal with an inner wall of a downhole casing and is anchored to the inner wall of the downhole casing; an internal channel is formed inside the collet body along an axial direction; and an inner wall of the internal channel of the collet body is a conical surface.