Objective： Investigating the effects of hairtail fishmeal on the quality of soy sauce koji. Method： Hairtail fishmeal was added to the preparation of Zhoushan traditional soy sauce koji， while changes in the numbers of the yeast colonies and Aspergillus oryzae spores were measured. Effects of hairtail fishmeal on the activity of koji protease in soy sauce were measured by Folin-phenol reagent method. Besides， effects of the hairtail fishmeal on the volatile components of the fermented soy sauce koji were investigated by gas chromatography-mass spectrometry （GC-MS）. Result： Adding appropriate amount of hairtail fishmeal promoted the growth of yeast and Aspergillus oryzae spores in the process of koji making（36 h）， especially the number of spores in each group reached more than 8.5×108. The protease activity in each treatment group was significantly higher than that in the control group（P＜0.05） except for 24 h. The amino nitrogen of soy sauce koji in each experimental group were higher than that in the control group for about 14.5%， 18.8%， and 19.4% in 30 h， respectively. There were 33 types of volatile components identified by GC-MS in each experimental group， among which， volatile components in the groups of 4% addition were 11.55% higher than that of the control group. Although the content was lower than that in the groups of 6% addition， there was a significant decrease in the components such as nonanal which could produce smell of fish. Conclusion： Adding appropriate amount of hairtail fishmeal can promote the growth of microorganism and the activity of protease in soy sauce koji. However， it did not show a significant effect on the colour， odor and fluidity of the soy sauce koji. Besides， it could also raise the content of the amino nitrogen. The addition of fishmeal had little effect on the kinds of volatile compounds in soy sauce koji， yet the excessive amount of fishmeal brought bad flavor to soy sauce koji.