The embodiment of the invention discloses a method and device for predicting the position of an oil-water interface. The method comprises the steps: calculating a first pressure gradient of a position where a first sample point is located through the obtained oil layer sampling data of the first sample point at a target layer of a to-be-measured region; calculating a second pressure gradient of a position where a second sample point is located through the obtained water layer sampling data of the second sample point at the target layer of the to-be-measured region, wherein the pressure of an oil layer where the first sample point is located is mutually connected with the pressure of a water layer where the second sample point is located; calculating the residual pressure of the position where the first sample point is located through sampling data of the oil layer and the determined pressure measurement reference plane of the to-be-measured region; and predicting the position of the oil-water interface through employing the oil layer sampling data, the first pressure gradient, the second pressure gradient, and the residual pressure. According to the technical scheme of the embodiment of the invention, the method can achieve the preliminary prediction of the position of the oil-water interface in an oil field which is lower in degree of prospecting.