Abstract: The variable Mach number waverider (VMW) is considered to perform well in the wide-speed range during hypersonic stage. However, when scholars compared it with the traditional fixed Mach number waverider (FMW), the constraints of identical planform shape and equal volume were not imposed. Accordingly, the previously illustrated advantages in wide-speed performance were not persuasive. In this paper, the VMW configurations were generated using the planform-customized waverider design method by giving leading-edge profiles. Meanwhile, the FMW configurations with identical planform shapes and equal volumes were also generated, and hence to explore whether the performance advantages of VMW in hypersonic wide-speed range existed. Computational fluid dynamic techniques were employed to analyze flow fields, providing preliminary explanations for the performances. Results showed that compared with the FMW with identical planform shape and equal volume, there were no superior advantages for the lift-to-drag ratios of the VMW in hypersonic wide-speed range. Moreover, the variable Mach number flow fields employed as basis flow fields and therefore the corresponding change of waverider surfaces hardly influenced longitudinal stability when the planform shape was fixed. We guess that the traditional waveriders using fixed Mach number flow fields themselves have satisfactory wide-speed performances in hypersonic stage. Consequently, improvement of the wide-speed performance for waveriders ought to focus on the subsonic, transonic and supersonic stages which dramatically deviate the on-design state, rather than hypersonic stage.