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An agricultural vertical takeoff and landing (VTOL) tailsitter UAV with symmetrical winglets and wings was designed. The main parameters of the taisitter, wingspan, wing root, wing slightly, sweep angle, winglet slightly, winglet slightly longer, winglet height, winglet sweep angle, winglet thickness and winglet length were investigated to study the relationship between the structural parameters and the endurance time. The 3D model of tailsitter and its outflow field were established with CATIA and ANSYS software. The outflow field of tailsitter was simulated by using computational fluid dynamics (CFD) software with model under 130 different structural parameter combinations. The feature factors of aerodynamic coefficients and weight coefficients were screened with the analysis of variance. Relationship between characteristic structural parameters and endurance time was established with the accuracy of 0.97. Four models of aircraft were processed by 3D printing technology for wind tunnel test. The aerodynamic coefficients of the aircrafts in cruise state were measured. The relative error between aerodynamic coefficient numerical simulation and wind tunnel test results was less than 14%. Simulation results were verified by measuring the endurance time in the fixedpoint hover of the two produced UAV samples. The result showed that the relative error was less than 15%, and the model can be used to optimize the design of structural parameters for the agricultural VTOL tailsitter UAV.