INTRODUCTION: The outbreak of COVID-19 caused by SARS-CoV-2 infection has become a serious hazard to global health. Apart from attacking respiratory system, it can induce multiorgan dysfunction, including cardiovascular system, liver, kidney, gastrointestinal, nervous system, and immune system. However, there are few reviews focusing on summary and comparison of diagnostic methods and complications induced by SARS-CoV-2 infection, which places a significant limit on the effective management. AREAS COVERED: This review is a blend of evidence obtained by literature retrieval from PubMed, clinical experience, and the authors' opinions. We searched PubMed using the terms 'COVID-19 & diagnosis' and 'COVID-19 & complications' and selected the most relevant articles. Here we summarize the diagnostic methods that are available in clinic and discuss their different characters. Furthermore, the review offers an insight into the symptoms, incidence, and clinical strategies of complications associated with SARS-CoV-2 infection. EXPERT OPINION: COVID-19 has been a global pandemic, which requires rapid response. The comparison between different characters of the diagnostic methods and the summary of the symptoms, incidence, and clinical strategies of complications given in this review are not only significant for the optimal use of diagnostic methods, but also beneficial for the prevention and management of complications.