The present study was conducted to investigate the effects of xylo-oligosaccharide (XOS) on plasma biochemical parameters and fatty acid composition of muscle in growing-finishing pigs. A total of 110 Duroc×Large White×Landrace pigs at 70 days of age with an initial body weight about 30 kg were randomly assigned to 11 groups with 10 pigs per group (male:female=1:1), and fed individually. The experimental groups consisted of control group (pigs were fed a basal diet), antibiotic group (pigs were fed the basal diet supplemented with 0.04 kg/t Stafac and 0.2 kg/t Acrasin), supplementation groups of 100, 250 or 500 g/t XOS during 30 to 65 kg stage (pigs were fed the basal diet supplemented with 100, 250 or 500 g/t XOS during 30 to 65 kg stage, and were fed the basal diet during 66 to 100 kg stage), supplementation groups of 100, 250 or 500 g/t XOS during 66 to 100 kg stage (pigs were fed the basal diet during 30 to 65 kg stage, and were fed the basal diet supplemented with 100, 250 or 500 g/t XOS during 66 to 100 kg stage), and supplementation groups of 100, 250 or 500 g/t XOS during 30 to 100 kg stage (pigs were fed the basal diet supplemented with 100, 250 or 500 g/t XOS). When the average body weight of pigs reached about 100 kg (about 170 days of age), blood samples were collected by precaval vein, and then plasma were obtained by centrifuge for analyzing biochemical parameters. The samples of longissimus dorsi (LD) muscle and biceps femoris (BF) muscle were collected and their fatty acid composition were measured. The results showed that, when compared with the control group, supplementation with 100 or 500 g/t XOS significantly decreased the daturic acid (C17:0) content of BF muscle during 30 to 65 kg stage (P<0.05); during 66 to 100 kg stage, supplementation with 250 g/t XOS significantly increased the content of saturated fatty acid (SFA)+monoun saturated fatty acid (MUFA) of BF muscle (P<0.05), and supplementation with 100 or 500 g/t XOS significantly increased the content of arachidomic acid (C20:1) of BF muscle (P<0.05); during 30 to 100 kg stage, supplementation with 100 g/t XOS significantly increased the ratio of oleic acid (C18:1n9) to linoleic acid (C18:2n6c) of LD muscle (P<0.05), as well as the contents of C20:1, MUFA and SFA+MUFA of BF muscle, supplementation with 100 or 250 g/t XOS significantly decreased the plasma total cholesterol concentration (P<0.05), and supplementation with 500 g/t XOS significantly increased the plasma high-density lipoprotein-cholesterol concentration (P<0.05). Collectively, these findings suggest that diet supplemented with several doses of XOS can increase the muscular contents of MUFA and SFA+MUFA by regulating plasma biochemical parameters related to fat metabolism, which improve the flavor and nutritive value of pork; dietary supplementation with 100 g/t XOS is optimal during 30 to 100 kg stage in growing-finishing pigs.