Promoting humus production by composting is meaningful for decreasing organic wastes pollution, and repairing contaminated environment. However, the interaction of multiple humus formation pathways has limited to understand how to improve humus formation by composting. Here, humus formation has been divided into biotic and abiotic pathways to quantify their synergy to humus formation. Monomolecular reducing sugars, amino acids and protocatechuic acid acted as precursors to simulate humus formation during composting in 20 days. PARAFAC analysis of humic acids structure presented that the humus formed by abiotic process was more complex and quicker. While two-dimensional correlation spectra illustrated that compounds derived from biotic process were steadier than the abiotic one. The core microorganisms which transform simple components into complex ones could explain it, which further illustrated that the microbial metabolism can effectively promote the complexity of humus either. Additionally, to analyze the contribution of biotic and abiotic pathways to humus formation, the synergy of the two pathways has been quantified. Abiotic synthesis, biotic degradation, and biotic synthesis were accounted for 30.68%, 43.58% and 25.74%. Therefore, promoting humus production by abiotic process may be an efficient way to reduce organic waste pollution with composting, especially for the protein-like and cellulose wastes.