| To study the regulation effect on vaccination of porcine circovirus-2 (PCV2) by co-delivering interleukin-12 (IL-12) cDNA via chitosan nanoparticles, two subunits of IL-12, P40 and P35 of Tibetan pig, were cloned into mammalian expression plasmid VR1020. VRIL-12 was transfected into HEK293 cells and PCR test was conducted. The results showed that IL-12 gene could express successfully. The recombinant plasmid was packaged into chitosan nanoparticles using ionic crosslinking method. The nanoparticles (VRIL-12-CNP) were confirmed to be nanoparticle size with good dispersion and positive charge. VRIL-12-CNP was then used to inoculate the 21-day-old piglets together with PCV2 vaccine. Blood samples were taken at day 0, 7, 14 and 28 post inoculation for analysis. The results showed that post vaccination the T cells such as CD3+, CD4+ , CD8+, and anti-PCV2 specific antibody, all increased significantly in the VRIL-12-CNP co-delivering pigs (P<0.05), the expression levels of TLR2, TLR7, IL-12, IL-4, IL-6 and IL-15 in the co-delivering group were significantly higher than those in control group (P<0.05), and the expression of STAT1, 3 and Bcl-2 gene was also increased significantly in the co-delivering pigs (P<0.05). Moreover, the net weight gain of the pigs in co-delivery group was significantly increased in the 28 days post inoculation (P<0.05). These results indicated that co-delivery of VRIL-12-CNP elevated swine innate immune response and both humoral and cellular immune response to PCV2, and VRIL-12-CNP is a promising safe and effective adjuvant to PCV2 vaccination.