The invention provides a method for preparing a liquid fuel from a coal petrography oil-gas reservoir, which comprises the steps: mixing coal powder with heavy oil, aging, thermally melting and dispersing to obtain oil coal slurry, and performing phase separation on the oil coal slurry to obtain liquid hydrocarbon, sol phase and gel phase, wherein the sol phase is cracked in a hydrogenation way, and the gel phase is coked. The method can obtain the qualified liquid fuel only by simply improving the existing refinery equipment, thereby avoiding the complex reaction process that the coal is directly liquefied and is indirectly liquefied. Therefore, the method realizes the development or the separation of the oil in the coal petrography oil-gas reservoir under the real mitigatory condition, thereby being low in investment cost and operation cost. The residue which is generated by the coal-oil co-treatment is subjected to the coking treatment, thus being good for environment and improving the yield of the liquid fuel.