The incidence of synchronous multiple primary malignancies is low. The presence of different lung tumor types in one patient is rare. Here, we report a rare case of synchronous lung squamous cell cancer and small cell lung cancer in a 60-year-old man. Because of the presence of two different tumor types, the proper treatment must be determined. To identify treatment targets, the genetic features of primary tumor tissues from the lungs were analyzed by next-generation sequencing (NGS). The objective was to analyze the origin and evolution of multiple primary lung cancers. NGS can find the genetic mutation sites of patients to guide treatment and promote the advancement of precision medicine. The effects of standard treatments were evaluated by response evaluation criteria in solid tumors. The results suggest that early treatment of synchronous multiple primary malignancies is a favorable outcome.