This study was conducted to evaluate the effects of different doses of xylo-oligosaccharide (XOS) replacing both antibiotics and zinc oxide (ZnO) on the growth performance, diarrhea rate and plasma biochemical parameters of weaned piglets, and to selected its optimal dose of dietary supplementation. A total of 150 weaned Duroc×Large White×Landrace piglets at 21 days of age were randomly assigned to five groups with 6 replicates per group and 5 piglets per replicate, representing blank control group (without antibiotics and zinc oxide), positive control group (containing antibiotics and zinc oxide) and 100, 250 and 500 g/t XOS groups, respectively. Daily feed intake and diarrhea were recorded for each pen. On days 1, 7, 21 and 56 of the experiment, the body weight of piglets in each pen were recorded, and the average daily feed intake (ADFI), average daily gain (ADG) and ratio of feed to gain were calculated, as well as sampling the blood of precaval vein to collect plasma for analyzing the biochemical parameters. The results showed as follows:1) the ADG of 100 g/t XOS group on days 8 to 21 and 1 to 56 of the experiment was significantly higher than that of blank control group (P<0.05), as well as the ADFI of 100 g/t XOS group on days 8 to 21, 22 to 56 and 1 to 56 of the experiment (P<0.05). 2) The diarrhea rates of 100 and 250 g/t XOS groups on days 1 to 7 of the experiment were significantly lower than that of blank control group (P<0.05), as well as of three XOS supplemented groups on days 8 to 21 of the experiment (P<0.05), but there was no significant difference compared with the positive control group (P>0.05). 3) On day 7 of experiment, the activities of aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) in plasma of 500 g/t XOS group were significantly higher than those of positive control group (P<0.05); on day 21 of experiment, the activity of alanine aminotransferase (ALT) in plasma of 100 and 500 g/t XOS groups was significantly higher than that of blank control group (P<0.05); on day 56 of experiment, the activities of ALT in plasma of 100 g/t XOS group, AST in plasma of 500 g/t XOS group and alkaline phosphatase in plasma of 250 and 500 g/t XOS groups were significantly higher than those of blank control group and positive control group (P<0.05), the activity of LDH in plasma of 100 g/t XOS group was significantly higher than that of blank control group (P<0.05), and the activity of α-amylase in plasma of 500 g/t XOS group was significantly higher than that of positive control group (P<0.05). These findings suggest that dietary supplementation with 100 to 250 g/t XOS can enhance intestinal health by regulating nutrient metabolism, reduce the diarrhea, and promote the growth of weaned piglets; with increasing age of the piglets, it may be appropriate to increase the supplementation dose of XOS.