Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused widespread transmission and been threatening health and lives due to high infectivity, acute progression and lacking of effective treatment. Both innate immunity and adaptive immunity are essential to defend against viral infection, while T cells function as a bridge of both arms and induce effective immune responses. Although traditional approaches demonstrate general features of T cells in COVID-19 patients, there are still a lot of unknown details to be characterized due to the complexity of SARS-CoV-2 infection. Single-cell RNA sequencing (scRNA-seq) technology is able to powerfully characterize gene expression at single-cell level and new subsets at district differentiation stage or with specific function. Here we have revealed the heterogeneity of the host T cells, including CD4 ⁺ T cells, CD8 ⁺ T cells, regulatory T (Treg) cells, natural killer T (NKT) cells, gamma-delta T (γδT) cells and mucosal-associated invariant T (MAIT) cells in COVID-19 patients with different clinical manifestations. T cell based therapeutic approaches, including enhancing virus specific T cell responses, reverting T-cell exhaustion and alleviating inflammation, are also discussed. This review provides insights into clinical treatment and vaccine design for SARS-CoV-2 infection.