Four composting treatments with different ratios of penicillin mycelial dreg (PMD) to sewage sludge (T-1, 1:0.4; T-2, 1:0.8; T-3, 1;1.2; T-4, 0:1) were investigated to characterize the property and composition of water-extractable organic matter (WEOM) and assess their stabilization via parallel factor analysis (PARAFAC) of fluorescence excitation-emission matrix (EEM). The results show that DOC, DON, DOC/DON ratio and respirometric rate decrease; SUVA(254) increase in four treatments. Penicillin degradation occurs mainly in the first 12 days. A five-component model was obtained, in which three protein-like and two humic-like components were identified. The maximum fluorescence intensity (F-max) of components is affected by the initial composition of treatments. Furthermore, the relationships between the WEOM parameters and the F-max of components in T-2 were established using Pearson correlation analysis, indicating that component 3, component 4 and component 5 are the effective parameters in evaluating the stability for composting PMD. To sum up, EEMs-PARAFAC can be proposed to evaluate stability during composting of PMD. (C) 2016 Elsevier B.V. All rights reserved.