With the increasing number of power electronic converters and servo motor driving systems being applied on more electric aircraft (MEA), they generally show the characteristics of constant power load, which influences the stability of power system. Therefore, the stability has gradually become the key to determine structure of power system of MEA. Based on the structure of high-voltage direct current (HVDC) power system in MEA, this paper mainly researches on the factors that have influences on transient stability of power system of MEA. Firstly, an advanced HVDC power model is established. Secondly, the influences of generator at different power scales in HVDC on stability through adopting large-signal method and the roles which each parameter of DC bus play in stability are analyzed. Lastly, theoretical analysis is implemented through Matlab/Simulink.