Due to the fact that the heterogeneity of some light oil reservoirs in the southern Bohai oilfield is strong and the difference of production in horizontal well section is obvious, the development effect of horizontal wells is poor. But there are few horizontal well test data at present. Aiming at the problem, the research and application of a new method for evaluating the production degree of horizontal well have been carried out using reservoir engineering methods. The theoretical relationship curve between water cut and recovery degree of horizontal well under different reservoir physical properties is calculated using multi-flow tube model. Based on this theoretical curve, the uneven production degree of horizontal section is qualitatively evaluated. On this basis, the permeability gradient and reserve proportion of low permeability section are used as the main controlling factors for the production degree of horizontal well, and a prediction chart of the remaining recoverable degree of the horizontal section is established. An evaluation parameters—the remaining recoverable degree of the low-permeability section—is introduced to quantitatively evaluate the production degree of horizontal well and the subsequent tapping potential. According to the tapping potential of remaining oil, the production degree of horizontal well can be divided into four types, corresponding to different potential tapping strategies. The research has been applied in the BZ oilfield, effectively guiding to tapping the remaining oil potential of horizontal wells. After the adjustment, the total daily oil production of BZ oilfield has been increased by 265 cubic meters per day.