The invention discloses an offshore seining cultivation device. The device comprises a mooring system, a buffer system, a head rope, a seine and a bottom anchor, wherein the mooring system consists of a main rope, a main anchor and an auxiliary rope; the buffer system consists of middle floaters and sandbags; head rope floaters pass through the head rope; the seine is positioned below the head rope and is provided with a vertical manrope, a horizontal manrope and a ground rope; and the bottom anchor is connected with the horizontal manrope. The device is characterized by also comprising a tensioning rope tied to the joint of the main rope and the auxiliary rope, wherein the other end of the tensioning rope is tied to the seine; the sandbags are tied to the tensioning rope; and a circle of waist floaters is arranged on the seine below the tie point of the tensioning rope and the seine. An anti-escape net is fixed on the inner side face of the seine between the horizontal manrope and the ground rope, and extends out of the seine, and the bottom of the anti-escape net is provided with an anti-escape ground rope. The device has the advantages of simple structure, convenient operation, effective prevention of the stack and wear of seines and the escape of the cultivation products, suitability for the seining cultivation in various offshore areas, and significant meaning and effect on the cultivation of various economic aquatic products.