Pectus excavatum is the most common chest wall deformity. Severe pectus excavatum can significantly impact both the physiological and psychological health of patients, necessitating timely therapeutic intervention. The Nuss procedure is currently the preferred surgical approach for treating moderate to severe pectus excavatum. However, in cases of severe pectus excavatum, the placement of the corrective steel bar through the anterior mediastinum poses a substantial risk of injury to the heart, major blood vessels, and lung tissue. This article reports a case of a 17-year-old patient with severe pectus excavatum combined with Marfan syndrome. CT examination revealed a Haller index of 14.07, with severe sternal depression leading to significant narrowing of the anterior mediastinal space and complete displacement of the heart into the left thoracic cavity, resulting in an extremely high surgical risk. We employed a simplified sternal elevation technique in conjunction with the Nuss procedure for treatment. During the operation, a sternal retractor was used to elevate the sternum, thereby enlarging the retrosternal space and facilitating the successful completion of the Nuss procedure. This approach effectively avoided damage to the heart and major blood vessels, resulted in no surgical complications, and achieved a satisfactory corrective outcome.