Water cone will form inevitably when natural energy is relied to exploit bottom-water reservoir by using vertical well. In order to analyze water flooding conditions and distribution of remaining oil around vertical well, it is necessary to quantitatively describe water cone shape. Established is a reservoir numerical simulation mechanism model according to actual formation parameters of a certain bottom water reservoir in Bohai Oilfield and it is considered that the ratio between vertical permeability and horizontal permeability, oil-water viscosity ratio, vertical well water-avoiding height and effective thickness and water cut of oil layer are main factors affecting water cone shape. Applied is mechanism model to quantitatively analyze the effect of single factor variation on the water cone shape, conducted is orthogonal design experiment of five factors and four levels, used is multiple linear regression method to conduct regression on experimental results and obtained is a quantitative description formula of vertical well water cone shape affected by multiple factors. Actual application shows that the results obtained by using formula to conduct quantitative calculation meet relative requirements.