The invention relates to an automatic retraction oil cylinder. The automatic retraction oil cylinder comprises a cylinder body, a piston rod, a cylinder head and a cylinder base respectively connected to two ends of the cylinder. The cylinder base is provided with an oil port in communication with the interior of the cylinder body. The automatic retraction oil cylinder further comprises a cylinder head connecting seat and a cylinder base connecting seat. The cylinder base connecting seat is disposed in the cylinder base, one end of the piston rod is arranged in the cylinder body, the other end penetrates the cylinder head and comes out of the cylinder body to be connected to the cylinder head connecting seat, the piston rod has a central through hole, a spring is disposed in the central through hole, and two ends of the spring are respectively fixed to the cylinder head connecting seat and the cylinder base connecting seat. According to the automatic retraction oil cylinder, the spring is disposed in the central through hole, one end of the spring is fixed, the other end can move along with the piston rod, the spring is extended and generates an elastic force when the piston rod stretches out of the cylinder body, so the piston rod retracts under the function of the elastic force of spring, retraction caused by deadweight or oil pressure is needless, the scope of application of the oil cylinder is enlarged.