Abstract: Kunming mice were infected by feeding 150±5 larvae of Trichinella spiralis, established was also a normal control group. Blood was collected from the ophthalmic venous plexus respectively on 7 d, 21 d, 35 d and 49 d after infection and IL-12 in the serum was detected by ELISA. The level of IL-12 in serum decreased in groups of 7 d, 21 d, and 35 d, with a significant difference to the control （P<0.01）. However, there was no significant difference between 49 d group and control （P>0.05）, suggesting that the serum IL-12 of the Trichinella spiralis-infected mice significantly decreased at the earlier stage but approached to normal at a later stage.

Key words: Trichinella spiralis, Mice, Interleukin-12