NOVELTY - Preparation of monolayer oxidized graphite alkene in large scale comprises oxidizing natural crystalline flake graphite with oxidant to obtain oxidized graphite; ultrasonically stripping and dispersing; filtering the unreacted graphite to obtain aqueous solution of oxidized graphite alkene; and adding to flocculating agent, settling, filtering, and drying to obtain the solid oxidized graphite alkene.    USE - The method is for preparing monolayer oxidized graphite alkene in large scale (claimed). The monolayer oxidized graphite alkene is used for constructing a two-dimensional optoelectronic element e.g. nano-computer chip, solar cell electrode, and field effect transistor.    ADVANTAGE - The method prepares the graphite alkene in large scale by flocculating, settling, and separating out the solid oxidized graphite alkene easily from aqueous dispersion liquid. It has easy material availability, convenient operation, simple technology, and good repeatability. Monatomic oxidized graphite alkene can be taken as flaky reinforced phase of composite material to prepare the material with high mechanical property and good obstructing performance, such as finger point collecting material.    DETAILED DESCRIPTION - Preparation of monolayer oxidized graphite alkene in large scale comprises:    (A) oxidizing graphite by taking 2-500 g natural crystalline flake graphite as raw material; oxidizing with oxidant (10-22 g) for 72-100 hours; using 1 L water to clean and filtering; cleaning to neutral; and drying to obtain oxidized graphite, where oxidant is prepared from 35 ml concentrated sulfuric acid, 18 ml concentrated nitric acid, and other agents i.e. potassium chlorate, potassium permanganate, phosphorus pentoxide, potassium peroxydisulfate, and/or hydrogen peroxide;    (B) dispersing and stripping by putting the solid oxidized graphite, which is deacidified and cleaned, into deionized water to dilute into 0.5 g/L; ultrasonically stripping and dispersing for 0.5-10 hours; filtering the unreacted graphite and collecting the filtrate to obtain aqueous solution of oxidized graphite alkene; and repeating the steps (A) and (B) for unreacted graphite; and    (C) flocculating and settling by adding to flocculating agent at 5-50 g/L to settle the oxidized graphite; filtering, freezing the filter cake, and drying to obtain solid oxidized graphite alkene, where flocculating agent is potassium hydroxide, sodium hydroxide, hydrochloric acid, sulfuric acid, nitric acid, potassium chloride, sodium chloride, sodium sulfate, potassium iodide, and/or polyacrylamide.