The invention provides a design method for a variable-Mach-number parallel wide-speed-range waverider aircraft based on the osculating-cone theory. Firstly, an upper surface trailing edge line and a shock wave outlet molded line of the waverider aircraft are given, then discrete configuration of the Mach number interval is designed, and a datum flow field is generated; and the designed Mach numberinterval is discretized through a certain discrete law, the discretized Mach number interval is matched with discrete points on the upper surface trailing edge line, and accordingly the discrete points on the upper surface trailing edge line can be subjected to streamline tracing in the datum flow field under the different Mach numbers so as to obtain a lower surface trailing edge line and a leading edge line, and accordingly the waverider aircraft with the variable-Mach-number waverider configuration is designed. According to the variable-Mach-number parallel wide-speed-range waverider aircraft, the defect of poor repeatability and reproducibility in an existing design scheme of a wide-speed-range waverider aircraft is overcome, the limitation that the shock wave surface of a cone-derived waverider aircraft can only be conical is broken through, the requirement for wider flight speed range and airspace is met, and the practicability of the waverider aircraft is further expanded.