Objectives To explore the efficacy of corticosteroid treatment in patients with severe COVID-19 pneumonia and the association between corticosteroid use and patient mortality. Methods A retrospective investigation was made on the medical records of the patients with severe and critical patients with COVID-19 pneumonia from January to February 2020. First, the patients who received corticosteroid treatment were compared with patients without given corticosteroid treatment. Then, a propensity score matching method was used to control confounding factors. Cox survival regression analysis was used to evaluate the effect of corticosteroid therapy on the mortality of severe and critical patients with COVID-19. Results A total of 371 severe and critical patients were included in our analyses. Two hundred and enine patients were treated with corticosteroid therapy. Most of them were treated with methylprednisolone (197[94.3%]). The median corticosteroid therapy was applied 3 (IQR 2-6) days after admission, 13 (IQR 10-17) days after symptoms appeared. Temperature on admission (OR = 1.255, [95%CI 1.021-1.547], p = 0.032), ventilation (OR = 1.926, [95%CI 1.148-3.269], p = 0.014) and ICU admission (OR = 3.713, [95%CI 1.776-8.277], p < 0.001) were significantly associated with corticosteroids use. After PS matching, the cox regression survival analysis showed that corticosteroid use was significantly associated with a lower mortality rate (HR = 0.592, [95%CI 0.406-0.862], p = 0.006). Conclusion Corticosteroid therapy use in severe and critical patients with COVID-19 pneumonia leads to lower mortality but may cause other side effects. Corticosteroid therapy should be used carefully.