Vaccinia virus is a kind of enveloped double-stranded DNA virus with a large molecular weight of 180 ~ 220 KB. Its genomic characteristics are as follows: (1) hairpin structure at the end of DNA; (2) reverse duplication at the end of 2)DNA; (3) There are conservative regions and variation regions. It can infect a variety of tissues with low integration rate and can be used for short-term gene expression. Vaccinia virus can infect resting cells, and the genes are not integrated on the host chromosome, so the overall capacity of foreign genes is large. The main disadvantage is that it can trigger an immune response, which makes repeated administration a problem. At present, a recombinant vaccinia virus vector is being developed, which can insert and express multiple genes, easily transfect various tumor cells and efficiently express the target genes.