Abstract: In order to reveal the underlying rules of small intestinal mucosal immunity in goat at different developing stages, 0.5, 2 and 12 months, respectively, the distribution and number changes of intraepithelial lymphocytes (IELs), goblet cells (GCs) and mast cells (MCs) were investigated by histological and histochemical methods.The results showed that the number of IELs and MCs were significantly increased (P<0.05) with age, while the number of GCs decreased substantially (P<0.05).On the other hand, the distribution of IELs was decreased from duodenum to ileum, and the number of IELs in duodenum and jejunum was 84.45% and 98.14% of ileum respectively at 0.5 month old. The distribution of MCs was similar to that of IELs. The number of GCs, however, increased from duodenum to ileum.The results suggested that GCs played a crucial defensive barrier role in the early postnatal period, while the effect of IELs and MCs enhanced concomitant with postnatal development of the gut mucosal immune system.