The invention relates to an underground anti-spraying device in an oil pipeline of a rod oil extraction system and a method. According to the technical scheme, an upper joint is connected with a connecting sleeve through a sliding sleeve; a lower joint is connected with the lower end of the connecting sleeve; the sealing is realized through the cooperation of a rod column sealing element of a sealing rod and a central pipe sealing surface on the upper side of a central pipe; the upper end of a sliding rod is arranged in the inner chamber of the sliding sleeve and is communicated with a hydraulic oil inlet formed on the upper joint; under the sealing effect of the sliding sleeve and the sliding rod, hydraulic control power directly acts on the upper end of the sliding rod; the sliding rod can freely slide in the sliding sleeve under the effect of the hydraulic control power, so that the conversion of liquid pressure and mechanism power can be realized; the pressurizing opening, pressure-releasing closing and sealing can be realized through the power stored by a spring. The invention has the beneficial effects that the contact between a metallic conical surface of the sealing rod and a rubber conical surface of the central pipe is utilized to realize the sealing, the pressurizing opening, pressure-releasing closing and sealing, the sealing manner is reliable, the rod sealing in the oil pipeline is realized and the problem of marine pollution caused by raw oil spraying can be prevented.