A lithium metal flow battery system and a preparation method for the same belong to the field of electrochemical power sources. A cathode of a lithium metal flow battery is made of slurry formed by mixing lithium metal powder or lithium alloyed powder with organic liquid electrolyte containing lithium salt, an anode of the lithium metal flow battery is made of mixed slurry formed by the same organic liquid electrolyte and carbon catalyst or carbon-loaded catalyst, high-purity oxygen saturated in the slurry serves as oxidizer, a polymer composite membrane for separating the anode from the cathode is arranged in the middle, a lithium ion migrates between the two electrodes by means of the organic liquid electrolyte and the membrane, and an electron flows on an external lead connected with the anode and the cathode and a load to generate current. The novel lithium metal flow battery can be continuously used only by means of circulating feeding, and lithium metal can be regenerated by recovering discharge products in anode slurry and reused as cathode materials. The lithium metal flow battery system has the advantages of high energy density, continuous and stable operation, simple structure, long cycle life, high safety, high power density, and capability of realizing quick charge and discharge.