Objective: To evaluate the severe illness incidence of, predictors for, and effects on outcome by COVID-19. Methods and Results: 104 patients with COVID-19 in the Harbin Infectious Disease Hospital from Jan 15 to March 22, 2020 was retrospective include, 16.53 developed severe illness COVID-19. Patients who developed severe illness were significantly higher body-mass index (BMI), number of comorbidities, lymphocyte percentage and electrocardiogram abnormalities (P < 0.0001). Multivariate logistic regression was used to determine the predictors of developing severe illness. Independent predictors of severe illness COVID-19 were BMI and electrocardiogram abnormalities (P < 0.05). The electrocardiogram abnormalities was associated with poor outcomes (include mortality, sent to ICU or transfer to a superior hospital) (odds ratio, 7.374; 95% confidence interval, 1.365-39.846; P < 0.05). Similar results were observed in BMI. Conclusions: The higher BMI and electrocardiogram recording abnormalities on admission are the predictor of prognosis severe illness patients with the COVID-2019.