The Main Landing Gear Bay(MLGB) lies in the belly of the fuselage wing body main landing gear opening. The structure of the area is complex, where the problem of external load, stress concentration, fatigue is the most serious, and where the body load transfer realizes the aim of regional balance. The MLGB compartment of the reinforcement is different from general body opening reinforcement. The one hand, the MLGB compartment of the reinforcement will be able to effectively alleviate the opening stress concentration, on the other hand, it will take part in the force among the main wing, landing gear and fuselage structure to reduce the surrounding stress. A good reinforcement option directly influences the wing body force and the main bearing structure design. The article based on force and finite element analysis discusses the reinforcement options of lowwing aircraft MLGB.