Dissolved organic matter (DOM) collected from a garage-type dry fermentation system was investigated using UV-Vis absorption and fluorescence spectroscopy. Spectral parameters A 253/203 , biological index and fluorescence index were used to assess the structural characteristics and sources of effluent DOM. The results showed that aromatic rings highly substituted with hydroxyl, carbonyl, ester and carboxylic groups were obtained in the aerobic decomposition stage, and microbially derived organic matter dominated in the dry anaerobic digestion process, suggesting that the hydrolysis of organic macromolecules (lignin) in the aerobic decomposition resulted in the formation of water-soluble intermediates which can be easily assimilated and metabolized by microbial cells in dry anaerobic digestion process. PARAFAC of the excitation-emission matrix spectra revealed five fluorescent components occurring in effluent DOM: four humic-like components (C1-C4) and one protein-like component (C5). The F max values of components 1, 2, 3 and 5 showed large fluctuation than that of component C4, suggested the formation and degradation of these components. Component C4, with high aromatic content and higher degree of humification, was more difficult to be utilized and degraded by microorganisms than other components. The PAR-AFAC-PCA displayed three PCA factors (factors 1, 2 and 3), which accounted for 34.51, 34.20 and 31.11 %, respectively, of the variance in fluorescent components. Humic-like component C4 showed positive factor 1 loadings. Factor 2 was mainly explained by the tryptophan-like component C5. The humic-like components 1, 2 and 3 concurrently showed a relatively high factor 3 loading. The PARAFAC-PCA in this study could separate the characteristics of the DOM fluorescent component namely the source strength of the humic-like components versus the contributions of protein-like components in the total fluorescence analyses.