Antimicrobial peptides (AMPs) are a class of defensive peptides synthesized or secreted by intestinal cells. It plays an important role in intestinal innate immunity in piglets. There are a variety of AMPs secreted by intestinal epithelia, such as ANG4, BD2, BD3, lysozyme, and RegIIIγ. To characterize the expression pattern of these AMPs, the mRNA expression level of porcine RegIIIγ, ANG4, BD2, BD3, and lysozyme in the duodenum, jejunum, and ileum of piglets from 0 to 5 weeks was analyzed by realtime quantitative PCR (realtime PCR). The results showed that the mRNA levels of all antimicrobial peptides  gradually increased after birth, but the expression level after weaning decreased, and then increased significantly. In addition, the most important antimicrobial peptides in the intestine are lysozyme and RegIIIγ, which means that the two antimicrobial peptides play an important role in the innate immunity of the intestinal mucosa.