The invention belongs to the technical field of material preparation and 
photocatalysis, and discloses a high-activity 
graphite-phase 
carbon nitride material and a preparation method thereof. The preparation method comprises the following steps: forming a self-generated gas 
atmosphere a gas generated from a precursor by 
pyrolysis in the high-temperature calcining process under the control on an 
inert gas, and guiding synthesis of a 
carbon nitride material, thereby obtaining a flaky porous 
graphite-phase 
carbon nitride material. According to the preparation method, after the 
inert gas is not introduced any longer, a self-generated gas generated from the precursor is relatively uniform at different parts, and the carbon 
nitride material prepared with the preparation method is uniform in morphology and relatively good in 
crystal form; due to the escape of the self-generated gas, the material is effectively pored, and thus the specific surface area and the active sites of the material are increased; due to the self-generated gas 
atmosphere, the 
polymerization degree of the precursor is reduced, and the obtained carbon 
nitride material has a relatively large amount of unpolymerized amino or imino groups. The preparation method disclosed by the invention is simple, efficient and low in cost, and the carbon 
nitride material prepared with the preparation method is excellent in 
photocatalysis activity and very good in practicability.