The human IL-2 cDNA was cleaved from pHIG53 and inserted in the intermediate vector pSP-72 which has the restriction sites comptible with clone site of the expression vector pDOR-neo, then IL-2 cDNA was directionally inserted into the retroviral vector pDOR-neo to construct a eukaryotic expression vector. The vector was trans feeted into human osteosarcoma cell line by lipofectin. The IL-2 was bioassayed in the culture of tumor cell after selection of G418. The production of IL-2 was 50～800 U per 1×10⁵ cells every 24h, which makes it possible to carry out osteosarcoma gene therapy.