Objective The immune responses of COVID-19 convalescent patients have not been well described. Methods Blood from thirty COVID-19 convalescent patients who were virus-free were collected. Their clinical laboratory findings and SARS-CoV-2-specific humoral and cellular immunity were detected. Results At 283 days after diagnosis of SARS-CoV-2 infection, the levels of clinical laboratory indicators and lymphocyte subtypes returned to normal levels. However, the ratio of memory/naive CD4+ T lymphocytes cells was greater in COVID-19 convalescent patients and severe COVID-19 convalescent patients, when compared with that in healthy blood donors (P=0.0135) and non-severe patients (P=0.0431), respectively. The levels of anti-SARS-CoV-2-IgM (P=0.014), S1-IgM (P=0.0004) and RBD-IgM (P=0.0002) in severe COVID-19 patients were all significantly greater than those in non-severe COVID-19 patients. When the serums of COVID-19 convalescent patients were diluted as 1:125, the predictive of serum neutralization capabilities were persistent in all patients. SARS-CoV-2-specific T cells were generated and maintained in majority of tested convalescent COVID-19 patients, regardless of the severity of disease in acute phase. Conclusion At 283 days after diagnosis of SARS-CoV-2 infection, specific cellular and humoral immunity against SARS-CoV-2 could be detectable. The severity of disease in acute phase cannot affect the strength of cellular and humoral immunity in convalescent phase.