Objective: Based on a thorough analysis of monotherapy (pembrolizumab) and chemoimmunotherapy, the immunomodulatory effects of chemotherapy agents are emphasized. Background: The combination of chemotherapy and immune checkpoint inhibitors should and is already being regarded as a new standard strategy for the first-line treatment of advanced NSCLC. As some scientists hold, chemoimmunotherapy is the beginning of a new era of lung cancer therapy. Scientists of this field are trying to make the perfect blend, that is, to explore the perfect condition for combination therapy. However, first, we should fully understand the specific role of chemotherapy agents in combination therapy and its specific mechanism. However, our current consideration of this aspect is not comprehensive enough. Based on a full understanding of the mechanisms and roles of these partner treatments, can the perfect blend or a more appropriate combination strategy of cancer immunotherapy be established? Methods: Search and discuss the literature of pembrolizumab in the treatment of non-small cell lung cancer, as well as previous studies on the immune regulatory function of chemotherapeutic agents, to analyze the mechanism of chemotherapeutic agents in combination immunotherapy. Conclusion: Here, we carefully analyzed the details of clinical trials of pembrolizumab in the treatment of NSCLC, and reviewed literature in this field. Therefore, we aim to put forward that chemoimmunotherapy is not a simple model of one plus another. Accordingly, we believe that the more likely role of chemotherapeutics in combination therapy with pembrolizumab is an immunomodulator. Based on this perspective, we propose that more attention and efforts should be devoted to understanding and exploring the immunomodulatory function of chemotherapy agents.