Oncolytic viruses (OVs) have been investigated for a century and have become one of the most advanced types of tumor immunotherapy. It is primarily a natural or genetically modified viruses, including DNA and RNA viruses. In recent years, with the rapid development of genetic engineering technology, the gene-modified oncolytic viruses have made great progress in the field of tumor treatment, several types of viruses (including HSV, adenovirus, poxvirus, measles virus, reovirus etc.) are currently in preclinical studies, clinical trials or have been approved in clinic, showing good safety and clinical efficacy. It is generally believed that oncolytic viruses target and kill tumor cells by selectively replicating themselves in tumor cells, and finally lysing and killing tumor cells. At the same time, they can stimulate the immune responses of the body, thus enhancing the antitumor immunity, the tumor cells can be targeted and killed with no obvious side effects. The combination of oncolytic virus and immune checkpoint by gene recombination and the breakthrough of tumor immunotherapy have made the application of oncolytic virus more extensive, however, there are still some bottleneck problems such as virus targeting, security and administration route. This review provides a comprehensive and detailed overview of the development of oncolytic viruses. We list some viruses have been used as candidates for lysis of cancer cells and the clinical trials in the field of oncolytic virotherapy. And we discuss about the immunological mechanism of oncolytic virus targeting to kill tumors, and the challenges and prospects in the future.