This study is conducted to investigate the effects of Achyranthes bidentata polysaccharide (ABP) as a dietary additive on growth performance, plasma parametre profile and the mRNA abundances of IGF-1 and IL-1β in liver, jejunal mucosa and mesentery lymph node. A total of 200 three-hybreded (Landrace×Yorkshire×Duroc) piglets weaned at 28 days of age were allocated into five dietary treatment groups on the basis of body weight and litter of origin in a complete randomised design. Five diets were tested for 35 days, including the basal control diet, the antibiotic treatment diet (basal control diet+500 mg/kg flavomycin), and three ABP treatment diets, in which ABP were added to basal control diet with 500, 1000 and 1500 mg/kg, respectively. There was higher average daily feed intake (ADFI) in animals fed with 500 mg/kg ABP when compared with animals in other groups (P<0.05). However, there was no significant deference in ADFI among animals in control group, antibiotics group (500 mg/kg flavomycin), high dose ABP supplementation group (1000 and 1500 mg/kg ABP) (P>0.05). Flavomycin (500 mg/kg) and different dose of ABP supplementation significantly increased average daily gain (P<0.05). Compared with animals in control group, there was low FiG in animals fed with 500 mg/kg flavomycin, 500, 1000 and 1500 mg/kg ABP, respectively (P<0.05). Flavomycin (500 mg/kg) and different dose of ABP supplementation significantly decreased the diarrhoea frequency of weaned piglets (P<0.05). Moreover, there was lower diarrhoea frequency in animals fed with different dose of ABP compared with animals fed 500 mg/kg flavomycin (P<0.05). Supplementation of ABP increased plasma concentrations of hormones, antibodies, and alkaline phosphatase (P<0.05) and IL-1β mRNA abundance in liver, jejunal mucosa and lymph nodes. These findings indicate that ABP is effective in improving growth performance and defending capacity, which suggests that ABP can be used as a diet additive for weanling piglets.