In the era of coronavirus disease 2019 (COVID-19) pandemic, imported COVID-19 cases pose great challenges to many countries . Chest CT examination is considered to be complementary to nucleic acid test for COVID-19 detection and diagnosis . We report the first community infected COVID-19 patient by an imported case in Beijing, which manifested as nodular lesions on chest CT imaging at the early stage . Deep Learning (DL) -based diagnostic systems quantitatively monitored the progress of pulmonary lesions in 6 days and timely made alert for suspected pneumonia, so that prompt medical isolation was taken . The patient was confirmed as COVID-19 case after nucleic acid test, for which the community transmission was prevented timely . The roles of DL-assisted diagnosis in helping radiologists screening suspected COVID cases were discussed.