Objective: To analyze the contents of different kinds of fatty acids in carotid atherosclerotic plaques. Methods: A total of 24 patients who underwent carotid endarterectomy at the Second Affiliated Hospital of Naval Medical University from October 2021 to September 2022 due to moderate and severe carotid artery stenosis were retrospectively enrolled, including 20 males and 4 females, with a median age[M(Q1, Q3)] of 68.5 (63.5, 72.3) years. According to the symptoms of cerebral ischemia, the patients were divided into a symptomatic group (12 cases) and an asymptomatic group (12 cases). Regarding the pathological characteristics, the patients were divided into a stable group (14 cases) and a vulnerable group (10 cases) according to carotid plaque pathology scores. The expression differences of different types of fatty acids in carotid plaques were analyzed by targeted fatty acid metabolomics technology based on ultra-performance liquid chromatography-mass spectrometry (UPLC-ESI-MS/MS) analysis. Results: In the 24 samples, the median amount of fatty acids [M (Q1, Q3)] was 1 113 (330, 5 897) ng/g. A total of 13 medium and long-chain fatty acids were detected, including saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids. The content of saturated fatty acids was 584 (290, 9 888) ng/g, accounting for the highest proportion of 51.8%. The content of polyunsaturated fatty acids was 1 444 (393, 4 264) ng/g, accounting for 44.4%. The content of monounsaturated fatty acids was 2 793 (1 558, 3 247) ng/g, accounting for 3.8%. The contents of linoleic acid, α-linolenic acid and oleic acid in carotid plaques in the symptomatic group were 1 760 (581, 3 006), 682 (527, 886) and 2 081 (1 358, 2 907) ng/g, respectively, which were lower than those in the asymptomatic group 3 149 (2 226, 4 683), 1 423 (964, 2 270) and 3 178 (2 352, 3 993) ng/g (all P<0.05). The contents of linoleic acid, α-linolenic acid and oleic acid in carotid plaques in the vulnerable group were 1 537 (588, 2 921), 649 (477, 850) and 2 081 (1 129, 2 831) ng/g, respectively, which were lower than those in the stable group 3 149 (2 047, 4 416), 1 423 (940, 2 184) and 3 091 (2 201, 3 973) ng/g (all P<0.05). There were no significant differences in the contents of 11, 14-eicosadienoic acid, γ-linolenic acid, eicosapentaenoic acid, arachidonic acid, erucic acid, margaric acid, pentadecanoic acid, stearic acid, dodecanoic acid and palmitic acid (all P>0.05). Conclusions: Saturated fatty acids are the main type in carotid plaques. The contents of oleic acid, α-linolenic acid and linoleic acid decrease in vulnerable plaques.