The invention relates to organic liquid fertilizer prepared from lentinan fermentation wastes. A preparation method of the organic liquid fertilizer comprises pretreating lentinan fermentation wastes,carrying out staged cooling, carrying out fermentation and adding accessories into the fermentation product to obtain a finished product. The lentinan fermentation wastes as raw materials are pretreated so that difficult-to-use substances in the wastes are degraded into nutrients easy to be utilized by plants. In fermentation, organic matters and nutrients in the wastes are increased and solids in the wastes are further degraded and can be easily absorbed and used by plants so that crop demands in different stages are satisfied. Bacillus megaterium, Bacillus mucilaginosus and Bacillus pumiluscan promote soil invalid phosphorus and potassium transformation. Trichoderma and white rot fungi can enhance the crop resistance to some diseases and improve a crop yield. The functional adjuvant compound sodium nitrophenolate and diethyl aminoethyl hexanoate (DA-6) can improve fertilizer efficiency and promote crop growth.