Objective: This study explored the effect of respiratory function training under the mode of mutual-help of patients to the postoperative pulmonary infection and immune function on lung cancer. Methods: 116 lung cancer patients who received surgical treatment from June 2018 to June 2019 were enrolled as the object. Patients were categorized into a control or observation group, according to the admission time of patients. Each group contained 58 subjects. The control-group was given regular nursing intervention, and the observation-group received respiratory function training under the mode of mutual assist between patients. Subsequently, the postoperative pulmonary infection, pulmonary function, and the changes of immune function before and after surgery were compared between the two groups. Result: The pulmonary infection rate of the group for observation was much lower than that of the control-group. The difference was statistically significant (5.17%, 17.24%, = 0.0394). The postoperative pulmonary function indexes in the observation-group were conspicuously better than those in control-group, the difference was statistically conspicuous (P<0.05). After nursing intervention, the cellular immune factors TNF-α, IL-8, and IL-6 of the two groups were conspicuously lower than those before the nursing intervention, and the decrease in the observation-group was remarkably greater than that in control-group, with the difference of statistical significance (P<0.05). In addition, the T cell subsets CD4+ and CD4+/CD8+ in the observation-group were conspicuously higher than those in the control-group. CD8+ in the observation-group was conspicuously lower than that in the group of control, with statistical significance (P<0.05). Conclusion: The respiratory function training under the mode of mutual-assist of patients can effectively reduce the incidence of postoperative pulmonary infection, improve the postoperative pulmonary function index, and improve the immune function, which is worthy of clinical promotion.