High levels of sulfur-containing odorous compounds can always be detected in waters during black bloom induced by aquatic debris. These contaminants are great threatens to water ecological security and human health. However, detailed reports focused on the sources and forming mechanisms of these odorous compounds were seldom seen. In this study, various aquatic debris like algae, zooplankton, fishes, benthic fauna and aquatic plants were used to simulate the occurrence of black bloom. Results showed that black bloom can be triggered by all of these aquatic debris. The highest levels of volatile organic sulfur compounds were detected in the added-algae treatments because of the high content of sulfur-containing amino acids in algae. Methionine was used as precursor of VOSCs during the experiment. Illumination and anaerobic conditions, especially illumination, were found to be more favorable for the degradation of methionine. Significant correlations were found between the degradation rate of methionine and the ammonium nitrogen levels, demonstrating that the first step of methionine degradation was deamination. The variations of several intermediate products (α-hydroxybutyric acid, α-oxobutyric acid and 4-methylthio-2-oxobutyric acid (KMBA)) in the degradation system were studied. The accumulation of KMBA was quite low compared to that of α-hydroxybutyric acid and α-oxobutyric acid. These results demonstrated that the demethylthio reaction happened with a short period of time after deamination. Or maybe these two reactions happened at the same time. Methanethiol was generated during this period and then transformed to dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide and H₂S through a variety of ways.