In COVID-19 disease caused by coronavirus SARS-CoV-2, blood lymphocyte percentage is suggested to be an indicator of disease progression. A Time-LYM% model (TLM) was established for disease classification and prognosis prediction. Patients have varying lymphocyte percentage after the onset of COVID-19. At 10-12 days after onset of symptoms, patients with lymphocyte percentage of more than 20% are classified as moderate moderate and may recover quickly. Patients with less than 20% lymphocytes in the blood are classified as severe. At the second time point 17-19 days after symptom onset, patients with more than 20% lymphocytes in blood are in recovery and patients with between 5% and 20% lymphocytes are in danger and those with less than 5% lymphocytes become critically ill with high mortality rate.