In 1982, a foreign gene successfully expressed in the vaccinia virus WR strain (mouse neurotropic strain) aroused a great concern of Chinese scientists. In 1984, Dr. ZHU Ji-Ming, academician of Chinese Academy of Science organized a collaborative research group in the Institute of Virology, Chinese Academy of Medical Science to develop a novel gene expression system based on vaccinia virus Tiantan strain which was used to prepare smallpox vaccine for human use more than 50 years in China. After more than ten years of effort, a highly efficient vector system for foreign gene expression was successfully established and widely used for the expression of foreign genes, for recombinant vaccines, and the development of monoclonal antibodies and diagnostic reagents. This paper briefly described the study and application of the gene expression system and discussed the problems and prospects of vector vaccine development.