With the continuous development of oilfield, bottom hole pressure is much lower than the saturation pressure, near the bottom of the oil well serious degassed, this will reduce the relative permeability of oil phase. In the process of production, after the production flow pressure drop to a certain limit, with the loss of the flowing pressure and the production to reduce instead, and it is no longer in line with common output prediction method, So by analyzing Daqing oilfield production data, it is concluded that the functional relation of reasonable flowing pressure and the peak production.