The present disclosure discloses flake metal lithium powder and a preparing method thereof; by ultrasonically pulverizing the metal lithium placed in a low-viscosity inert organic resolvent using a vacuum ultrasonic pulverization method, a micrometer scale flake metal lithium powder is prepared. The metal lithium powder may be used as an anode material for a lithium cell or lithium ion cell. The present method has advantages of high product purity, simple operation, low processing temperature, low cost, high efficiency, and less demanding on equipment, etc., and has a high prospect of being applied to mass production of metal lithium powder.