Viral encephalitis is the result of the virus's effect on the central nervous system, which can involve any age group from children to the elderly, and the severity of the disease depends on the type of virus and the host′s immune system. The pathogens causing viral encephalitis are various and have different clinical manifestations. Laboratory examination, imaging and cerebrospinal fluid analysis plays vital role in the diagnosis of encephalitis. In the past, ELISA was the most commonly used method for the diagnosis of viral encephalitis, but most of viral encephalitis could not be diagnosed by etiology due to the low type of detection reagent and high price. With the continuous improvement of molecular biology technology such as PCR and its application in the detection of cerebrospinal fluid pathogens, which has become an effective tool for the diagnosis of viral encephalitis. This paper reviews the etiology, pathogenesis, diagnosis and treatment of viral encephalitis.