To learn the effects of microorganism, light and aeration action on the inhibition of straws on HABs algae and explore the chemical composition related to the inhibition, eight conditions involved in autoclaved or not, airproof or oraerated, light or dark were set up, and chemical compositions and inhibitory effects of extracts obtained under these eight conditions on the growth of Phaeocystis globosa were analyzed. The results showed that the antialgal activities and components of extracts under various conditions were different. Even for the extracts under the same conditions, significantly changes in inhibitory action and components were shown with the development of soakage. The extracts obtained under the not-autoclaved, oraerated and light conditions, respectively had not always higher inhibitory activities than those obtained under the autoclaved, airproof and dark conditions. These suggested that microorganism, light and aeration action had important roles in the inhibition of straws, which were responsible for the differences in inhibitory action and components of extracts under the different conditions. However, microorganism, light and aeration action, respectively, did not always facilitate the inhibition. In most extracts with high antialgal activities, the levels in phenols and fatty acids were higher. However, in some cases, the extracts with lower phenols and fatty acids had high antialgal activities, whereas the extracts with weak antialgal activities had high levels of phenols and fatty acids. These indicated that phenols and fatty acids maybe played an important role in the inhibitory effect of straw, and that some algal promoters and algaecides other than phenols and fatty acids, existed in extracts.