The application of electric unmanned aerial vehicles (UAVs) in agricultural remote sensing monitoring is limited by their short endurance. A long-endurance battery-powered light blended-wing-body UAV was designed for agricultural remote sensing. A design method for a light blended-wing-body UAV was proposed. The structural parameters of the light fixed-wing UAV was optimized and a model was built. The aero-dynamic performance of the UAV was determined by computational fluid dynamics (CFD), and the force distribution in flight state was dynamically analyzed based on fluid-structure interaction model. The results showed that the lift-to-drag ratio of the optimized model was 2.6% higher than that of the initially designed model, and the light blended-wing-body UAV had good aerodynamic characteristics. The pressure distribution of the UAV was effective at a 6° angle of attack and a cruising speed of 15.5m/s. When the take-off weight was 1.5kg, the maximum value of pressure on the lower surface of the UAV was 143Pa, and the lift force was mainly concentrated on the leading edge of the wing. The theoretical endurance time was 65min, and the maximum stress during the cruising phase was lower than the tensile strength of the fuselage material and the yield strength of the rotor. Under the same conditions, the maximum value of total deformation was 0.28838mm. The above parameters all met the normal working conditions of the UAV. Therefore, the structure, materials, and performance of the proposed light agricultural remote sensing UAV were suitable for agricultural remote sensing. It also provided a design method and key technologies for the application of electric drones.