Abstract: Antarctic krill frozen powder and degreasing powder were digested by sequence-grade trypsin separately. The enzymatic hydrolysate were filtrated by ultrafiltrate membrane then detected by LC-Q-TOF. Differential peptides were found before and after degreasing process and verified by triple quadrupole mass spectrometer. Results showed that, four petides were identified and lost during the processing of Antarctic krill into defatied shrimp powder. Two petides were derived from the arginine kinase of Antarctic kill, they were EDMELQK, ASVHVDLPGWAK, DQVSEALLK and LQNAEGEVAALNR. The former two were from arginine kinase and the later two were from tropomyosin. This paper could provide theoretical basis for the application of mass spectrometry to analyze the peptides of Antarctic krill.