The invention relates to biomass fuel, in particular to a preparation method of high-heating-value oxygen-containing biomass fuel. Catalytic powder is prepared from raw materials including tantalum hydroxide and a phosphoric acid solution, a fermentation product is prepared from straw, grass seed shells, corncobs and other raw materials and treated, a fermentation broth is obtained, the catalyticpowder is added, the mixture reacts, a solid product is obtained and put in a sodium hydroxide solution, sedimentation particles are obtained through a reaction, the sedimentation particles and polysiloxane are mixed and compressed, and the high-heating-value oxygen-containing biomass fuel is obtained. Cellulase in Shuizhang longan is used, the obtained biomass fuel contains very high carbon through a reaction process, the obtained biomass fuel has higher heating value, polysiloxane and alkyl pentanoate in the biomass fuel can be decomposed in the combustion process to release oxygen, so thatthe interior of the biomass fuel is sufficiently combusted, generation of pores is promoted, the heat efficiency of the biomass fuel is improved, and the application prospects are broad.