Abstract: In this paper, the boundary correction coefficient was introduced to characterize the influence of channel widths on the productivity of horizontal wells. In this way, the large evaluation results caused by the short duration of the drill-stem testing (DST) can be avoided, and the productivity of horizontal wells in narrow channel reservoirs can be accurately evaluated. A model for the horizontal well in narrow channel reservoirs was built and solved, and the variation curves of the boundary correction coefficient with testing time were obtained under different channel widths. The research results suggest that a narrower channel is accompanied by a smaller boundary correction coefficient, and hence, the impact of channel widths on the productivity of horizontal wells cannot be neglected. The method was applied to predict the specific productivity index of Well P1H and Well P7H, two horizontal wells in Bohai X Oilfield, and the relative error between predicted results and actual results was less than 5.4%. This indicates that the introduction of the boundary correction coefficient can significantly raise the productivity evaluation accuracy of ho-rizontal wells in narrow channel reservoirs. This method can provide a theoretical basis for predicting the productivity of horizontal wells in similar narrow channel reservoirs and guide the reasonable proration of oil reservoirs.