The invention provides an efficient biogas slurry fertilizer and a preparation method thereof. The efficient biogas slurry fertilizer is prepared from, by mass, 32%-57% of biogas slurry, 10%-32% of ammonium nitrate phosphate, 5%-27% of urea, 9%-15% of potassium nitrate, 5%-7% of ammonium sulphate, 5%-13% of ammonium dihydrogen phosphate, 0.5%-2% of borax, 0.74%-3% of EDTA magnesium, 0.4%-1.5% of EDTA zinc, 0.4%-1.5% of EDTA manganese, 0.08%-0.15% of DA-6 and 5%-7% of potassium fulvate. The efficient biogas slurry fertilizer is prepared by utilizing fruit and vegetable waste anaerobic-fermentation substrate biogas slurry, healthy development of green agriculture is also achieved while the biogas slurry utilization way for solving the gradual output increase problem is provided, and the problems of environmental pollution, resource shortage and planting safety of big cities are solved. Compared with direct biogas slurry application, the biogas slurry fertilizer is more comprehensive in nutrition and higher in content, reaches the standards of NY1106-2010 humic acid-containing water-soluble fertilizers, different forms of nitrogen sources are combined, and nitrate nitrogen, ammonium nitrogen and amido-nitrogen in the nitrogen sources can be organically combined and blended according to different crops and different climates, so that the fertilizer efficiency is higher and longer, the utilization rate is higher, precipitation and crystallization are not likely to occur, and the stability and a usage effect are good.