The invention discloses preparation of a biomass emulsion separation membrane. A preparation method comprises following steps: coprinus comatus powder treated with an alkali and sodium alginate are dispersed in water fully so as to obtain a mixed solution, and the mixed solution is subjected to stirring reaction at 20 to 30 DEG C for 10 to 20min so as to obtain a reaction solution; the reaction solution is subjected to vacuum filtration using a microfiltration membrane, is washed with deionized water, and is dried so as to obtain the biomass emulsion separation membrane. The biomass emulsion separation membrane possesses special superhydrophilic/under water super oleophobic and super oleophylic/under oil hydrophobic performance, is capable of realizing selective separation of oil-in-water emulsion and water-in-oil emulsion via infiltration of a continuous phase, and separation efficiency is higher than 99.0% after a plurality of times of circulation. The raw materials of the biomass emulsion separation membrane are cheap and easily available; the preparation process is simple; operation is convenient; cost is low; and large scale production and application can be realized.