The manned multi-rotor aircraft has the characteristics of large structural size, large load demand, and variable size and variable number of available rotors. The rapid determination of the power unit of this type of aircraft has strong engineering practicability. This article takes the design of a single-man multi-rotor aircraft as an example, collects data of more than 100 sets of matching schemes recommended by the brand's official website, uses exhaustive calculations and obtains the relationship between nine sets of parameters. Based on this, the rotor and equivalent circuit models are established, and the maximum working voltage of the 22 optimal motors is used to calculate the maximum matching rotor size and the number of rotors required by the optimization formula. The results show that the optimized selection scheme is more accurate and efficient. This method can be used to obtain a power unit scheme quickly with high weight efficiency, high endurance, and low cost, and pave the way for the detailed design of the subsequent manned multi-rotor aircraft.