The invention discloses an oil extracting and water injecting well head device. The device comprises a small cross connector and a large cross connector. A slider is arranged on the outer wall of the bottom end of the small cross connector. A transverse slide way is arranged at the top end in the large cross connector. The left side and the right side of the top end of the transverse slide way are both provided with a vertical slide way. A clamping groove is formed in the center of the top end of the transverse slide way. A conical face is arranged at the bottom end in the small cross connector. A conical hole is formed in the bottom end of the transverse slide way. A groove is formed in the right end of the inner wall of the large cross connector. A triangular cone is arranged at the left end of the groove and connected with the groove through a spring. According to the oil extracting and water injecting well head device, the small cross connector and the large cross connector are tightly connected by means of matching of the slider, the clamping groove, the conical face and the conical hole, the conical face and the conical hole are in butt joint, the joint of the small cross connector and the large cross connector can be tighter, petroleum makes contact with the triangular cone and makes contact with the bevel of the triangular cone through impacting force of petroleum so that the triangular cone can passively stretch, backflow is intercepted, and safety performance is improved.