TECHNOLOGY FOCUS - BIOLOGY - Preferred Method: The step (a) comprises (a1) crushing raw ore, sieving until the grain diameter is 50-150 mm, and conveying into X-ray sorting machine, (a2) controlling the potassium content in the ore to be more than 8% by a microcomputer of the X-ray sorting machine and processing the ore at a flow rate of 10-50 ton/h, and (a3) milling the ore grain to 150-200 meshes, sieving and conveying into a microwave processor. The step (b) comprises (b1) adding water into a microwave reactor, controlling the power of the microwave to be 900-1000 W, processing for 5 minutes, conveying the microwave processed water into an assembly chamber and a fermentation chamber, and (b2) microwave processing the potassium enriched ore grain at a microwave power of 900-1400 W for 30-60 minutes, and conveying into assembly chamber and fermentation chamber. The step (c) comprises (i) preparing complex microbial inoculum by taking Bacillus mucilaginosus (AS1.231, GIMCC GIM1.15) on a solid culture medium of pH 7.2 comprising 0.2 g potassium dihydrogen phosphate, 0.8 g dipotassium hydrogen phosphate, 0.2 g magnesium sulfate heptahydrate, 0.1 g calcium sulfate dihydrate, trace amount of sodium molybdate dihydrate, 0.5 g yeast extract, 20 g mannitol, trace amount of ferric chloride, 15 g agar and 1 l distilled water in 30 degrees C constant temperature incubator, activating for 2-3 days, culturing in a fermentation culture medium of pH 6.8-7.2 comprising 10 g sucrose, 0.5 g yeast extract, 0.5 g ammonium sulfate, 0.1 g magnesium sulfate, 0.1 g potassium chloride, 0.1 g disodium hydrogen phosphate, 1 g calcium carbonate and 1 l distilled water at 30 degrees C, culturing in a shaker incubator at a speed of 200 revolutions per minute for 5-6 days to obtain Bacillus mucilaginosus bacterial liquid, culturing Bacillus megaterium (AS1.459, GIMCC GIM1.14) on a solid medium of pH 7-7.2 comprising 5 g peptone, 3 g beef extract, 5 g sodium chloride, 20 g agar, and 1 l distilled water at 30 degrees C in a constant temperature incubator, activating for 2-3 days, fermenting in a culture medium of pH 7-7.3 comprising 10 g glucose, 0.5 g ammonium sulfate, 0.3 g magnesium sulfate heptahydrate, 0.3 g sodium chloride, 0.3 g potassium chloride, 0.3 g ferrous sulfate heptahydrate, 0.3 g manganese sulfate heptahydrate, 5 g calcium phosphate and 1 l distilled water at 30 degrees C in a shaker incubator at a speed of 200 revolutions per minute for 5-6 days to obtain Bacillus megaterium bacterial liquid, mixing the two bacterial liquids, and effective microorganism (EM) preparation to obtain microbial inoculum, (b) mixing the fermented material and microwave processed ore in a weight ratio of 1:1 to obtain a mixed material, where the fermented material comprises wheat bran, rice bran, waste molasses and soybean cake powder in a weight ratio of 1:1:2:1, mixing the mixed material and microwave treated water in a weight ratio of 1:1, adding 10-25% EM preparation based on the total volume of the fermentation substrate, and stacking to ferment for 10-20 days, (c) transferring the solid fermented product into a biological leaching device, adding sterile water higher than the solid fermented product by 5-10 cm, adding 10-25% microbial inoculum, adding water to a height of 5- 10 cm above the solid fermented product once in every 2-4 days, collecting the extract, and leaching for 20-30 days. The method further comprises concentrating the bioleachate to obtain liquid fertilizer having potassium content of 10-15 g/l, where the liquid fertilizer is reinforced with inorganic element to obtain multi-element liquid fertilizer and the solid part dried at less than or equal to 30 degrees C and granulated to obtain solid potassium fertilizer, and the resulting solid potassium fertilizer is reinforced with other elements to obtain biological potassium complex fertilizer. ACTIVITY - Fertilizer.