This invention discloses a method for separating biomass organic components. The method comprises: washing classified raw materials, decomposing in a high-pressure reactor under the actions of microwave and ultrasonic wave, and extracting organic components from biomass with 20-70 vol. % aqueous solution of an organic solvent. The separation process comprises: (1) extracting low-temperature-soluble organic component from biomass at 40-120 deg.C under 0.4-0.6 MPa; (2) separating cellulose pulp at 160-220 deg.C; (3) separating acetic acid, lignin and furfural from the liquid (separated by solid-liquid separation) by centrifuge and precipitation. According to different plants, the powers and frequencies of microwave and ultrasonic wave, as well as the reaction temperature and time can be adjusted. The method has such advantages as low organic molecule loss, little change, no harm of the products, high cellulose purity (higher than 95%), low lignin residue (not higher than 2%), and no environmental pollution.