The invention discloses a method for preparing superfine diamond single crystal micro powder. The method comprises the following steps: by taking diamond micro powder obtained by a mechanical crushing method as a seed crystal, uniformly dispersing the seed crystal on the surface of a silicon-based substrate by adopting a process for uniformly dispersing the diamond seed crystal through photoresist ultrasonic vibration, wherein the granularity of the diamond micro powder is M0/1-M6/12; depositing the silicon-based substrate on which the seed crystal is sowed by adopting hot filament chemical vapor deposition, and thus obtaining diamond single crystal particles; and treating the obtained diamond single crystal particles by combining chemical etching of the silicon-based substrate with a high-speed particle centrifugal sedimentation process, thereby obtaining the superfine diamond single crystal micro powder. With the adoption of the method, the superfine diamond single crystal micro powder can be obtained.