The aim of this study was to elucidate protein autolysis in Antarctic krill (Euphausia superba) after capture on fishing vessels and the maintenance of product quality. Under laboratory conditions, frozen Antarctic krill was used to verify the correlation between non-protein nitrogen (NPN) content and the degree of protein autolysis. The stability of NPN content during 90-days storage at –20℃ was also examined. Fresh Antarctic krill, complete in form or broken because of compression during trawling of the Antarctic krill fishing vessel were selected. The NPN content of Antarctic krill samples at different storage times were measured. The results showed that the NPN content of Antarctic krill had a good correlation with protein autolysis, and there were no significant changes in the NPN content during the 90-day of storage. Therefore, NPN was suitable for evaluating changes in the quality of Antarctic krill after capture. There was no significant change in NPN content during the first hour after the death of the captured Antarctic krill. However, the NPN content increased rapidly afterwards. Antarctic krill should be frozen or processed as soon as possible after capture. Compression during trawling damaged Antarctic krill and accelerated protein autolysis. Thus, the method of trawling used during Antarctic krill fishing requires improvement.