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The transition state is the most critical and dangerous state of the VTOL fixed wing aircraft in the whole flight process. In this paper, a transition corridor for a distributed propulsion VTOL fixed-wing aircraft is studied based on the lift characteristics of the wing and the power constraints of the power unit. Firstly, according to the sliding flow theory, the dynamic characteristics models of the lift fan system in the front part of the fuselage and the distributed duct system in the rear part of the fuselage were established by introducing the influence factor of the duct, and verified with the test data. Secondly, according to the lift characteristics of the wing, the transition curves of the aircraft at different angles of attack are calculated, in which the transition curves corresponding to the zero-lift attack angle and stall attack angle constitute the lift characteristics transition corridor of the distributed propulsion VTOL fixed-wing aircraft. Finally based on the dynamic performance of the power unit model, calculate the lift characteristic transition each state point in corridor corresponding power demand, according to the power limit of the lift fan system, distributed duct system and power unit total power limitation, get distributed to promote vertical take-off and landing a fixed wing aircraft power limitation in lifting features and power unit under the condition of complete transition corridor. The final results show that the minimum forward velocity is inversely proportional to the attack angle. The power required by the tail distributed duct system will exceed the limit when the aircraft is in low speed and small dip angle transition. For the power limit boundary required, the power limit condition of individual component is stricter than the total power limit condition. The research results of this paper can provide some reference for the transition corridor research of such VTOL fixed-wing aircraft, and on this basis, the subsequent work such as parameter sensitivity analysis and control system design of transition corridor can be carried out.