In order to reduce the problem of limited flight time of UAVs due to limited energy, it is necessary to study the operational energy consumption of agricultural UAVs during flight. Taking agricultural multi-rotor UAV as the research object, the white-box modeling method was used to construct the total flight efficiency model of agricultural UAV according to the principle of each component of the power system, and then an operational energy consumption model was established for agricultural UAV according to the flight characteristics of agricultural UAV, and the data obtained were verified by grouping tests of three dynamic parameters, namely speed, load and range of agricultural UAV. The results showed that the model had a high accuracy, with a maximum average error of about 6.582% and a median maximum absolute error of about 7.654%. Finally, each parameter of the model was analyzed and the model correction coefficient was introduced to correct the model, and the accuracy of the corrected model was reduced by about 3.092 percentage points of the maximum mean error and about 3.612 percentage points of the median error compared with the maximum mean error before the correction, which was significant after the correction. The theoretical model constructed can be used for the calculation and prediction of agricultural UAV operation energy consumption, and the corresponding operation energy consumption can be obtained and optimized before planning the UAV mission, and it can also be adapted to other rotor models with different controllers, which had certain application value.