The promotion effect of exogenous addition of Maillard precursors on rice straw decomposition process was evaluated from the perspective of humus composition in view of the stimulating effect of Maillard reaction precursors on the humus formation during rice straw decomposition. In this study, the indoor culture method was adopted, rice straw serving as the basic material based on the exogenous addition of three Maillard precursors (Catechol, Cat; Glucose, Glu; Glycine, Gly). The change of humus composition revealed the different effects of each precursor on the decomposition process of rice straw. The results showed that, the total organic C (TOC) content of Cat, Glu, Gly treatment and CK showed a decreasing trend with the extension of cultivation time, and the addition of three Maillard reaction precursors all promoted the mineralization of TOC, among which the effect of glucose was the most, making the TOC content decreased by 22.9%. After the culture, each treatment was beneficial to the increase of C content of humic-extracted acid (C_HE) and the complication of humic-extracted acid (HE) molecular structure. The addition of catechol could increase C_HE the most (475.4%), followed by the glucose, and glycine made the molecular complexity of HE the highest. The addition of three kinds of Maillard reaction precursors could increase the C content of humic-acid (C_HA) and improve the humus quality. In contrast, among the Maillard reaction precursors, the glucose was more favorable in increasing the C_HA content and improving the humus quality. To sum up, the glucose had more advantages in promoting the mineralization and decomposition of rice straw, improving the C_HA content in the decomposition process of rice straw and improving the humus quality. The catechol was more conducive to the improvement of C_HE content, while the glycine was more likely to promote the complication of HE molecular structure.