Abstract: In order to clarify the characteristics of the flow structure in the downstream entrance area of the navigation lock, so as to realize the quantitative prediction of the navigable flow conditions, a numerical simulation method was used to carry out the calculation of the navigable flow conditions based on the generalized model of the entrance area. Meanwhile, the flow structure characteristics and flow condition distribution law in the entrance area were analyzed. Based on the sensitivity analysis of the inflow velocity, inflow angle, and geometric parameters of the entrance area, a prediction formula for the extreme velocity in the downstream entrance area of the navigation lock was proposed. The results show that the flow structures in the downstream entrance area of the navigation lock is in a two-dimensional form and the prediction formula for the extreme velocity obtained by the regression analysis is reliable according to the verification results of the actual measured data of the specific engineering model. The proposed prediction formula is convenient and efficient, which provides a new approach to the prediction of navigable flow conditions in the downstream entrance area of similar navigation locks.