PubMed and Web of Science were used to search for related articles. The key words are “2019-nCoV” “COVID-19” “SARS-CoV-2” “clinical characteristics” and “laboratory findings”. To ensure the comprehensiveness and accuracy of the study, we also consulted the references of the included literature. The searches were performed three times to identify articles published before April 27, 2020. Then we screen the articles according to the abstract, eliminate the articles that obviously do not meet the inclusion criteria, and then read the full text for re-screening. Articles that provided values of laboratory indicators for severe and non-severe patients, including blood routine, inflammatory factors, biochemical and immune-related indexes were included. Pre-printed articles are also included. Articles published repeatedly, translated articles, studies did not include the laboratory indicators needed for meta-analysis; research data were missing were excluded. In addition, conference summaries, reviews and meta-analysis were excluded.