To investigate the early changes of peripheral blood leukocyte differential counts in patients with COVID-19. Ten patients with COVID-19 and 30 patients with other viral pneumonia (non-COVID-19) admitted to The Sixth People's Hospital of Shanghai and Jinshan Branch Hospital from January 22 to February 17, 2020 were enrolled in this study. The differential counts of white blood cells (WBC) were analyzed. Patients in COVID-19 group showed relatively lower absolute WBC count 4.95(3.90,6.03)x10(9)/L, lymphocyte absolute count 1.20(0.98,1.50)x10(9)/L and eosinophil absolute count 0.01(0.01,0.01)x10(9)/L. Leukopenia developed in two patients(2/10), lymphocytopenia also in two patients(2/10). Seven over ten patients presented with eosinophil cytopenia. In non-COVID-19 group, absolute WBC count was 8.20(6.78,9.03)x10(9)/L (P<0.001), lymphocyte absolute count 1.75(1.20,2.53)x10(9)/L(P=0.036), eosinophil absolute count 0.02(0.01,0.03)x10(9)/L(P=0.005). Lymphocytopenia occurred in 16.7% patients, eosinophil cytopenia in 16.7% patients too. In conclusion, leukopenia, lymphocytopenia and eosinophil cytopenia are more common in COVID-19 patients than those in non-COVID-19 patients.