Abstract: Since the beginning of the new century, advances in understanding the intricate interactions between oncology and the immune system have accelerated the rapid development of immune checkpoint inhibitors for the treatment of non-small cell lung cancer. However, resistance to immunotherapy is inevitable. Therefore, uncovering the mechanisms of immunotherapy resistance, proposing strategies to overcome resistance, and identifying future research directions are imperative. Given the limitations of space in each article, this review will explore the complex mechanisms underlying immunotherapy resistance. These mechanisms involve almost all cell types within the body, excluding foreign cancer cells. Notably, these cells serve as recipients (either inhibitory or stimulatory, or both) and producers of signals, playing different roles in various contexts. At the molecular level, these mechanisms include genetic and epigenetic abnormalities in all cells within the microenvironment, as well as the influence of a variety of protein kinase, growth factors, and cytokines with temporal and spatial heterogeneity. At the macroscopic level, host factors such as nutritional metabolism, comorbidities, and microbiota within the organs, as well as neuro-psychological regulation, influence the efficacy of immunotherapy.