Abstract: At present, in drilling design and evaluation, the shape of hydraulic flushing hole is usually equivalent to cylinder, which is one of the important bases to determine the effective extraction radius. However, the shape of hole is subject to the joint action of many factors, so the scientific nature of the equivalent shape to cylinder remains to be discussed. By adopting the factors of gravity, friction, water force and in-situ stress of coal and rock mass, and introducing the parallel Bergmark-Roos equation and PKN model, the BR-PKN equation describing the pore shape is established, and the pore shape is reconstructed by MATLAB. In order to verify its accuracy, data are collected and analyzed by using YZD18.5 logging tool in the field, and the hole section is drawn. The equivalent ellipsoidal and cylindrical holes are simulated by COMSOL. The results show that the shape of the holes drawn by MATLAB is ellipsoid with different three axes. The shape of the drawn hole is basically consistent with that in MATLAB. Compared with cylindrical holes, the extraction radius, desorption surface area and effective extraction volume of quasi-ellipsoid holes are 93%, 80% and 117% respectively, which provides a basis for drilling layout.