The invention relates to a disease-resistant slow-release rhizome biomass functional fertilizer and an application thereof. The biomass functional fertilizer comprises the following substances in parts by mass: biomass ash, wood vinegar, bone soup, ammonium lignosulfonate, sulfonated pine needle, urea, ammonium sulfate, diammonium phosphate, potassium sulfate, borax, zinc sulfate, polyaspartate potassium, attapulgite and compound sodium nitrophenolate. According to the invention, wood vinegar and dried biomass ash are mixed, the pH value of the biomass ash is reduced to lower than 9, and the decomposition problem when a ammoniacal nitrogen fertilizer meets the biomass ash can be solved; the bone soup provides microbe in protein active soil, the ammonium lignosulfonate has complexation/sequestration effect, provides ammoniacal nitrogen fertilizer and potassium element utilization rate in the fertilizer, and increase the trace element complexation capability, sustained capability and utilization rate of the trace elements such as calcium, magnesium, iron, copper, zinc, and manganese in the biomass ash, the movement distance of the phosphor element in the soil is developed from 4 cm to 8 cm, and the plant root development is promoted. The usage amount of the biomass ash is increased in the fertilizer, high nitrogen compound fertilizer is researched and developed, the pH value of the compound fertilizer is kept at 8-8.5, soil cidifying due to large application of the inorganic compound fertilizer is prevented, and the balanced fertilization is realized.