Objective To explore the effects of adjuvant treatment of modified Shashen Maidong decoction on immune function and adverse reactions of patients with lung cancer (Yin deficiency and internal heat syndrome).Methods 106 patients with nonsmall cell lung cancer (NSCLC)(Yin deficiency and internal heat syndrome) were randomly divided into control group and observation group with 53 cases in each group. Control group was given GP regimen chemotherapy (cisplatin injection+ gemcitabine hydrochloride), and observation group was given adjuvant treatment of modified Shashen Maidong decoction on the basis of control group. The clinical efficacy of the two groups was compared. TCM symptoms scores, Tcell subsets levels and adverse reactions were observed before treatment and after 8 weeks of treatment. Results The clinical total effective rate and stable rate of lesion in observation group were significantly higher than those in control group［(52.83% and 83.02%) vs (32.08% and 62.26%)］ (P＜0.05). After treatment, the scores of cough, bloody phlegm, fatigue, upset and sleeplessness, lowtemperature and night sweats, and dry stools of TCM symptoms scores were significantly decreased in the two groups (P＜0.05), and the changes in observation group were significantly greater than those in control group (P＜0.05). After treatment, the Tcell subsets indexes found that the proportions of CD3+and CD4+and CD4+/CD8+were significantly increased in observation group (P＜0.05), and the proportion of CD8+was significantly increased in control group (P＜0.05), while the CD4+/CD8+value was decreased(P＜0.05), and the difference between groups was statistically significant after treatment(P＜0.05). The incidence rates of myelosuppression, gastrointestinal reactions and infection were 15.09%,5.66% and 0.00%respectively in observation group, which were significantly lower than those in control group with 32.08%,22.64% and 9.43%(P＜0.05). Conclusion Modified Shashen Maidong decoction assisted with GP chemotherapy for patients with NSCLC (Yin deficiency and internal heat syndrome) can have significant efficacy. It can effectively improve the related symptoms, and enhance the immune system function, and has few adverse reactions in clinical application.