Abstract: Drill stem test (DST) in offshore oilfields lasts short. The evaluation results are, to some extent, uncertain, if the DST data of short time is used to evaluate the productivity of oil wells. In order to determine the DST productivity correction coefficient more accurately, a directional well was taken as the research object in this paper. The transient well test technique was introduced to set up relations between test time, boundary condition and stable productivity. Then, a new method for calculating DST productivity correction coefficient that is general for the actual oil reservoirs with various boundaries was developed and compared with the previous formula calculation method. It is indicated that the relation between the correction coefficient and the test time is affected comprehensively by oil reservoir parameters and boundary conditions. As for short-time test, the correction coefficient decreases with the decrease of fluidity and drainage area. As for the low-fluidity oil reservoirs with closed boundary, the correction results of the new method are more different from the calculation results of existing methods, and the new method is more accurate. The case study results show that the correction coefficient calculated by the new method is accordant with the actual situation. What’s more, the new method is applicable in wider range than the formula calculation method and its application value is higher.