Abstract: A fluid separating device includes a cylinder; a plurality of separators disposed around the cylinder; a first elastic piece disposed between one of the separators and the cylinder and applying an elastic force to the separator outward in a radial direction of the cylinder; a mandrel passing through the cylinder axially and configured to reciprocate between an expanded position and a contracted position in an axial direction of the cylinder; an elastic energy storage device slidably passing through the cylinder along the radial direction of the cylinder, the elastic energy storage device having one end connected to the mandrel and another end connected to the separator, the elastic energy storage device being configured to apply another elastic force to the mandrel in a direction from the contracted position to the expanded position; a first locking structure disposed on the cylinder; and a second locking structure disposed on the mandrel.