COVID-19 has raised worldwide concern as spiraling into a pandemic. Reports about comprehensive investigation of COVID-19 viremia are extremely scanty. Herein, we present four COVID-19 patients with positive SARS-CoV-2 nucleic acid test in blood, accounting for 12.12% of 33 detected cases. Rapid deterioration of these cases with septic shock, accompanying with lung CT images enlarged rapidly, decrease of blood oxygen, heart rate drop (with asynchrony of hypoxemia) accompanied with SARS-CoV-2 viremia. It indicates that massive replication and releasing into blood of SARS-CoV-2 and secondary inflammation storm may lead to injury of multiple organs and poor prognosis. So, positive COVID-19 nucleic acid test in blood may be a good forecasting marker of rapid deterioration of COVID-19 pneumonia. In addition, clearance of viremia may indicate tendency for recovery.