A boy, aged 6 years and 11 months, was admitted due to nephrotic syndrome for 2 years, cough for 1 month, and shortness of breath for 15 days. The boy had a history of treatment with hormone and immunosuppressant. Chest CT after the onset of cough and shortness of breath showed diffuse ground-glass opacities in both lungs. Serum (1,3)-beta-D glucan was tested positive, and the nucleic acid of cytomegalovirus was detected in respiratory secretions. After the anti-fungal and anti-viral treatment, the child improved temporarily but worsened again within a short period of time. Pneumocystis jirovecii was identified by Gomori's methenamine silver staining in bronchoalveolar lavage fluid. The child was diagnosed with severe pneumonia (Pneumocystis jirovecii and cytomegalovirus infection), acute respiratory distress syndrome, and nephrotic syndrome. After anti-infective therapy with sulfamethoxazole/trimethoprim and ganciclovir and respiratory support, the child still experienced progressive aggravation of dyspnea and tension pneumothorax, and extracorporeal membrane oxygenation (ECMO) was given on day 13 of invasive ventilation. Anti-infective therapy with sulfamethoxazole/trimethoprim, ganciclovir, and linezolid, anticoagulation therapy, sedation therapy, nutrition, and comprehensive management of the respiratory tract were given during ECMO. The child was successfully weaned from ECMO after 72 days, resulting in a length of hospital stay of 134 days. The child was followed up for 6 months after discharge, and there was a significant improvement on lung CT, without organ dysfunction. It is concluded that Pneumocystis jirovecii pneumonia is a potential lifethreatening infection for children with low immunity, and that ECMO can effectively improve the prognosis of children with severe respiratory distress syndrome.