The invention relates to a method for improving filtering quality of coal slurry water by compounding biological and nonbiological flocculants for coal. According to the method, a coal biological flocculant Bacillus subtilis solution culture raw liquor or white-rot fungi solution culture raw liquor and a coal nonbiological flocculant polyacrylamide (PAM) are compounded in a volume ratio of 1:X as biological and nonbiological flocculants. 8-14 mL of a 2 wt% coagulant aid CaCl2 water solution is added into the coal slurry water, the biological and nonbiological compound flocculants are added, and the pH value of the coal slurry water is regulated to 6-8, thereby improving the filtering quality of the coal slurry water floc under the biological and nonbiological synergistic actions. The method obtains favorable filter aiding effects, obviously lowers the specific filtration resistance of the coal slurry water floc, reduces the consumption of the coal nonbiological flocculant, lowers the restriction of various factors to the filter aiding effects, widens the applicability of the compound flocculants, and lowers the problems of environmental pollution and the like caused by the use of the chemical filter aids.