The effects of ultra-high pressure (UHP) (0.1, 100, 200, 300, 400, and 500 MPa for 10 min) treatments on the quality of grass carp (used as the raw material) were investigated. A number of parameters were examined, including total viable counts, total volatile base nitrogen (TVB-N) values, thiobarbituric acid (TBA) values, texture, color difference, microstructure, volatile odor, and taste. The results showed that total viable counts of grass carp were reduced significantly by UHP treatment. With increasing pressure, TVB-N values declined, whereas TBA values increased. After 300 MPa pressure treatment, TVB-N values decreased by 12.09%, while TBA values increased by 0.7 times. When the pressure exceeded 200 MPa, hardness and chewiness increased pronouncedly, with their values increasing by 0.87 and 2.22 times, respectively, at 500 MPa pressure. Total color difference gradually increased with increasing pressure. When the pressure exceeded 200 MP, the L* value and whiteness were markedly enhanced. Scanning electron microscopy (SEM) demonstrated that the overall surface structure of grass carp muscles with UHP treatment tended to be uniform and compact. The electronic nose and electronic tongue analyses showed that the volatile odor of grass carp treated with > 300 MPa pressure noticeably changed, whereas the taste profiles of grass carp treated at 200, 400, and 500 MPa pressure differed slightly from that of the control group. In conclusion, 300 MPa treatment might be appropriate for the processing and storage of grass carp as the TVB-N values rise at a slower rate at this pressure during cold storage, extending the shelf life from 10 days to 16 days.