The present invention discloses a CpG-ODN having a specific immuno-stimulatory effect on pigs and an application thereof. A nucleotide sequence of the CpG-ODN is shown in SEQ ID NO:1. The CpG-ODN canimprove induction of innate immunity and specific humoral and cell-mediated immune responses of the pigs, and can be transferred into a plasmid vector pFAR4 to construct a recombinant plasmid pFAR4-CpG to prepare a preparation containing the recombinant plasmid pFAR4-CpG. The preparation can effectively activate natural immune functions of the pigs, also successfully replaces or partially replaces antibiotics as an immune activator, can also effectively activate acquired immune functions of the pigs, especially cellular immunity, can be used as an immune adjuvant to improve a protective effect of vaccines, also has little toxic and side effects on body, has great potential, can be widely used in live pig breeding industry, and is conducive to reducing breeding cost, reducing incidence ofthe pigs, and improving survival rate and breeding efficiency.