A watertight, through wall connector has a tubular body, an O-ring and a holder. A neck is formed on one end of the body has to be bent to hold the holder. With such a connector, the neck is not easily cracked during the pressing process, and the deformation of the body will not occur. This can provide a watertight seal. In addition, the O-ring can fully expand by means of being squeezed between the inside wall of the reservoir and the holder. This can provide a watertight seal due to the full expansion of the O-ring.