A complex oil circuit with connected bending type of an aeroengine accessory gearbox was taken as the research object.The three-dimensional flow field inside the oil circuit was simulated and analyzed,and a one-dimensional mathematcial model was established.Based on the calculation results of the flow field,the reason for the insufficent oil flow at the inlet of the oil circuit of the accessory gearbox was found and the optimization scheme was determined.The results show that due to improper nozzle structure design of this aeroengine,the local flow area in the oil circuit structure of the accessory gearbox is small,and the local resistance loss is large,resulting in a smaller lubricating oil flow rate at the inlet of the oil circuit.By optimizing the nozzle structure and increasing the flow area in the oil circuit structure is increased,which effectively increases the flow rate of imported lubricating oil,and meets the design requirements.For the optimized accessory gearbox oil circuit,the area with the largest pressure loss is in the orifice section of each nozzle,but the pressure of each pipe flow section changes little,and the pressure distribution of the whole oil circuit is more reasonable.The mathematical model of pressure-flow in the gear box was established,which provided data support and reference basis for the selection and matching of lubricating oil volume flow rate under different inlet pressures.