Objective To summarize the diagnosis and treatment of synchronous multiple primary malignant tumors in lung. Methods The clinical and pathological data of 5 cases with intrapulmonary synchronous multiple primary cancer, who were diagnosed in recent 10 years in Xinhua Hospital, were retrospectively analyzed. Results The incidence of intrapulmonary synchronous multiple primary cancer was 0. 21%( 5 /2380) in all lung cancer cases diagnosed in respiratory department of Xinhua Hospital. There were 4 males and 1 female, with the average age of 60. 2 years old. Five patients were all treated with surgical operation. Four patients with bilateral synchronous multiple primary lung cancer underwent staging operation treatment( larger lesions on one side of lung underwent conventional thoraceotomy and lobectomy, and smaller lesions on another side underwent thoracoscopic lobectomy or wedge resection afer 1 month) . For 1 patients with ipsilateral synchronous multiple primary lung cancer, simultaneous operation was performed. There was no death during perioperative period or severe cardiopulmonary complications. They were followed up for 3 years. The survival rate was 80. 0%( 4 /5) at 1 year and 60. 0% ( 3/5) at 3 years, respectively. Conclusions With the development of medical science and awareness of pulmonary multiple primary cancer, early diagnosis improves continuously. Active treatment with operation can achieve better prognosis.