Provided is a flora for degrading sludge and removing foul smell and a usage method thereof. The compound flora includes, by weight, 10%-12% of thiobacillus denitrificans, 1.3%-5% of salt resistant bacteria, 2.6%-3.9% of nitrous acid leafy bacteria, 2.1%-3% of filamentous sulfur bacteria, 3.2%-4.0% of bifidobacterium, 1.3%-2.6% of nitrogen-fixing bacteria, 2.6%-3.2% of filamentous bacteria, 2.1%-2.6% of rhizobia, 2.6%-4.0% of iron bacteria, 1.3%-2.6% of cyanobacteria, 5.3%-6.6% of thermophilic bacteria, 5.3%-7.4% of halophilic bacteria, 0.5%-2.6% of sulfur producing bacteria, 1.3%-2.6% of oilphilic bacteria, 10.6%-21% of lactobacillus, 5.3%-9.2% of saccharomycetes, 7.9%-15.9% of bacillus, 2.6%-5.3% of actinomycetes, 1.3%-2.6% of photosynthetic bacteria and 3.2%-4.8% of high-temperature aerobic bacteria.