The effects of substitution of cinnamyl aldehyde for aureomycin and bacitracin zinc in nursery pig diet were studied. A total of 180 42-day-old healthy three-way crossbred (Duroc×Landrace×Yorkshire) nursery pigs were selected and divided into the control group, the experimental groups A and B according to the similar weight and the same sex ratio. Each group had 60 pigs with 4 replicates and 15 pigs per replicate. The pigs in control group were fed the common diet containing aureomycin, bacitracin zinc and colistin which used on the pig farm, while the pigs in experimental groups A and B were respectively fed the common diet substituted 400 or 600 mg/kg cinnamyl aldehyde preparation for aureomycin and bacitracin zinc. The feeding experimental period was 21 d. This experiment found that substitution of cinnamyl aldehyde for aureomycin and bacitracin zinc in nursery pig diet significantly decreased the diarrhea rate and diarrhea index of the pigs (P<0.05). Compared with the control group, average daily gain of pigs in the experimental groups A and B were raised, and the experimental group B reached a significant level (P<0.05). The serum total protein content of pigs in experimental group B was increased significantly (P<0.05); the serum glutamic pyruvic transaminase activity of pigs in the experimental groups was decreased, and that in group B reached a significant level (P<0.05);the serum aspertate aminotransferase activity of pigs in the experimental group B was significantly higher than that in control group and experimental group A (P<0.05); the activities of superoxide dismutase, catalase and glutathion peroxidase and total antioxidant capacity in serum of pigs in the experimental groups A and B were increased significantly (P<0.05) or very significantly (P<0.01); and serum malonaldehyde content of pigs in the experimental groups A and B was decreased very significantly (P<0.01). The levels of CSFV-Ab, PRRSV-Ab and PCV-Ab of pigs in the experimental groups A and B were significantly increased compared with control group (P<0.05); PRV-Ab level also got a rising trend and the experimental group B reached a significantly higher level (P<0.05). There were no significant differences of serum FMDV-Ab level among three groups (P>0.05). In conclusion, the substitution of cinnamyl aldehyde for aureomycin and bacitracin zinc in nursery pig diet is feasible and has better effects. The cinnamyl aldehyde can well prevent and control diarrhea occurs, enhance antioxidant capacity, promote the growth, and improve feed conversion of pigs. The optimum supplementary amount of cinnamyl aldehyde preparation in nursery pig diet is 600 mg/kg.