Great progress has been made in therapeutic virus for cancer. The development of molecular biology techniques has greatlyenhanced research on some properties of virus in host-specific, in gene site-specific integration and in oncolysis. It is possible to build up an engineering virus which will be safer and more efficient as an anticancer agent bymodification of virus surface proteins to get strong affinity to cancer cell, by deletion of oncogene from oncogenic virus or of special pathogenic gene to reduce pathogenicity of virus，and by inserting certain anticancer gene such as a silencer to centain gene site based on specificity of target cell and certain virus species. Besides，compared with other gene therapy，another special advantage is that virus DNA can automultiply replicate itself in host，which has a characteristic of cascade amplification for compensating primary dosage when the dosage is deficient.