TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The prepared seed medium comprises 1000 ml of potato juice, 20 g of saccharide, 20 g of agar and 30 g of lanoline. The prepared fermentation medium comprises 1000-2000 (preferably 1000) ml of potato juice, 90-200 (preferably 90) g of saccharide, 60-150 (preferably 60) g of agar and 80-150 (preferably 80) g of lanoline. Preferred Method: The step of selecting the strain comprises: (1) collecting soil sample on wool-washing waste dumpling place and the cholesterol production factory; (2) fetching 1 g of the above collected soil sample and then putting into a sterilized test tube, adding 10 ml of sterile water, oscillating and shaking uniformly by a vortex oscillator, standing the mixture for few minutes, fetching the supernatant, dripping on the seed medium, painting uniformly by a glass rod, putting into a 27 degrees C constant-temperature incubator to culture for 2-5 days, growing bacterial colony in the plates, picking out the mono-bacteria to a new seed medium, and judging the pure strain according to the morphological features and then numbering and storing; (3) inoculating the dozens of strains obtained from separation on seed medium, growing bacterial colony, fetching 1 g of medium under the bacterial colony to put into a test tube, adding 10 ml of chloroform and then shaking to make the possible cholesterol in the medium fully dissolved, and adding 10 ml of sulfuric acid and then observing, where if the chloroform layer presents blood red, the strain has conversion capacity and if not develops blood red, the strain has not conversion capacity; and (4) culturing the strain obtained from screening on a seed medium, if the bacterial colony texture presents impact and the surface is the tighter woolen-shape or solid, dried and multi-wrinkled, the strain is initially guessed as actinomycetes, and picking the bacteria to prepare a slide and then observing under a microscope, if the bacteria presents branched wire shape, the bacteria is ensured as actinomycetes. The method comprises putting the actinomycetes obtained from screening into a fermentation culture medium to perform fermentation, fetching the medium under the bacterial colony to the test tube with plug, adding 50-100% of ethanol and then fully shaking, adding ethyl ether and then shaking, adding petroleum ether and then fully shaking, standing to make the liquid layer separated, fetching an upper layer organic phase, blowing to dryness by nitrogen, and dissolving by 50-100% of ethanol and then repeatedly crystallizing. The fermentation step is carried out at a temperature of 20-50 degrees C (preferably 30 degrees C) and a pH of 6-8.5 (preferably 7.6) for 70-160 (preferably 110) hours.