Abstract: The fatty acid composition in grass carp muscle and their content changes during cooling preservation at 2-4℃ were studied using gas chromatography-mass spectrometry (GC-MS).The muscular fat in grass carp was found to contain large amounts of unsaturated fatty acids. The ratios of SFA: MUFA: PUFA and ω-6 PUFA: ω-3 PUFA were 1.08:2.19:1 and 5.65:1, respectively, which agreed well with the intake standards of fatty acids recommended by Chinese Nutrition Society. During cooling preservation, the total lipid contents and the relative contents of MUFA and PUFA in grass carp muscle were decreased gradually. Conversely, the relative contents of SFA were gradually increased. The degradation of fatty acids followed the rules that their degradation rate and extent were positively related with their unsaturation level and their structure types; the degradation of ω-3 PUFA taken place much earlier than ω-6 PUFA but the degradation rate of ω-6 PUFA was much faster than that of ω-3 PUFA. The relative contents of some long chain unsaturated fatty acids (LPUFA) were increased slightly with the extension of the cold storage time. These results indicated that in order to keep the nutritive values of grass carp muscle and extend its shelf life, it would be very important to control the degradation of muscular fatty acids during preservation processes.