The invention provides a composite microbial biogen capable of degrading organic waste efficiently and a preparation method and applications thereof. The composite microbial biogen contains Bacillus circulans, Bacillus subtilis, Alcaligenes faecalis and Penicillium diversum. The composite microbial biogen can be used with activated sludge for the existing sewage treatment equipment under the synergetic effect, the yield of excess sludge can be greatly reduced, the aims of emission reduction and energy saving can be realized and the sludge problem which is difficult to overcome for a long time in sludge treatment is effectively solved and the biogen has importanct economic importance and environmental importance and is suitable for each sewage treatment plant. The composite microbial biogen can also be used to prepare organic wastewater purifying agents, activated sludge enhancers of urban domestic wastewater and deodorants used in tipping sites, public places, agricultural product market, kitchens, bathrooms and the like.
