A nano gallium nitride spherical powder preparation method is characterized by including the following steps: putting a gallium oxide powder into a microwave heating device full of ammonia gas, and carrying out a reaction, to obtain a gallium nitride powder; and then carrying out ball-milling crushing of the gallium nitride powder, carrying out sieving treatment, and then carrying out induction plasma treatment to obtain the nano gallium nitride spherical powder. Compared with the prior art, the two-step method is adopted for preparation of the high-quality nano gallium nitride spherical powder, that is to say, the primary gallium nitride powder is prepared by the microwave solid-phase synthesis method firstly and then is further deeply processed through the induction plasma method; therefore, the purity of the gallium nitride powder can be improved, the powder can be nanocrystallized, and the gallium nitride powder with good dispersibility and high quality is obtained.