Abstract: An oil-tight coupling device includes a hose, an oil-tight gasket, a coupling sleeve, a coupling bushing and a nut. The coupling sleeve is provided with a plurality of equidistantly spaced apart resilient portions that bend inwardly. Each resilient portion has a protruding lip radially disposed at a lower end and a stop piece axially disposed at the lower end. The stop piece is provided with an inclined surface at either side. The coupling bushing is provided with a plurality of projections at an upper end for matching the resilient projections and a curved slot at a lower portion for receiving a stop post of said coupling sleeve to restrict the displacement of the coupling sleeve. By means of the stop post that displaces along the curved slot, the stop pieces may move along the inclined surfaces of the projections to cause the resilient portions to bend inwardly, allowing the lips to enter a neck portion of the hose to quickly secure the hose.