Abstract: A sufficient comprehension about the oil/air two-phase flow in the bearing chamber of an aero-engine is important for the design of its lubrication and secondary air system. The oil/air two-phase flow conditions in the bearing chamber can be studied via flow pattern classification, which is a feasible way to reveal the physical nature of two-phase flows in bearing chambers. However, flow pattern classification is difficult to perform directly by experiments owing to the extremely complex flow conditions in the bearing chamber of an aero-engine. Therefore, it is worthwhile to determine the flow pattern according to the difference of characteristic flow parameters. The oil-gas two-phase flow pattern in bearing chamber of aero-engine may include homogeneous flow,stratified flow and film/gas (oil particle-phase)flow.This article gives a contribution to this subject. An analytical approach is adopted to study the diversities of lubricant pressure and velocity and their distributions under different flow patterns. Furthermore, the influences of rotational speeds, oil flows and sealing air flows on these differences are investigated. The work indicates that lubricant pressure and velocity in the bearing chamber can be regarded as robust characteristic parameters to determine the flow pattern.