In order to analyze the cause of poor oilcollecting efficiency of intershaft bearings of a certain type of aeroengine,a threedimensional transient simulation model of oilgas twophase flow of bearing oilcollecting structure was established by multiphase flow numerical calculation method based on VOF model and slip grid technology.The flow field and oil distribution of the oilcollecting structure were calculated,the mechanism of oil movement and the mechanism of oilcollecting loss in the oilcollecting structure were revealed,and the influence of oil flow on oilcollecting efficiency was given.The results show that the counterflow and vortex ring in the oilcollecting structure are formed in the oilcollecting structure.The main reason for oil collection loss is that the oil droplets formed after the oil column impinges on the cage wall are carried into the slit between the oil dam and the collector by the vortex,and then thrown out to the bearing cavity,resulting in a decrease in oilcollecting efficiency.The oilcollecting efficiency of the oilcollecting structure is independent of the oil flow rate,and depends only on its own structure.The oilcollecting efficiency of the oilcollecting structure studied in this paper is 62%,so the oilcollecting structure must be improved to improve its oil collecting efficiency.