Objective To study the effects of Icotinib hydrochloride tablets combined with Gemcitabine and Carboplatin on cellular immune function and serum levels of tumor markers in patients with non-small cell lung cancer (NSCLC). Methods A total of 89 patients with NSCLC admitted to our hospital from December 2021 to October 2023 were selected, and they were divided into control group (46 cases) and observation group (43 cases) according to different treatment schemes. The control group was treated with Gemcitabine+Carboplatin, and the observation group was treated with Icotinib hydrochloride tablets combined with Gemcitabine+Carboplatin. The clinical efficacy, cellular immune function (CD3+^{, CD4}+^{, CD4}+^/CD8+^), the levels of tumor markers[carbohydrate antigen 199 (CA199), cancer antigen 125 (CA125), cytokeratin fragment antigen 21-1 (CYFRA21-1), carcinoembryonic antigen (CEA)], transforming growth factor-β1 (TGF-β1), vascular endothelial growth factor (VEGF), and the incidence of toxic and side effects were compared between the two groups. Results The total effective rate of the observation group (93.02%) was higher than that of the control group (78.26%) (P<0.05), and there was no significant difference in the incidence of nephrotoxicity, myelosuppression and leukopenia between the two groups (P>0.05); after treatment, the levels of CA199, CA125, CYFRA21-1, CEA, TGF-β1, VEGF were decreased, and the improvement in the observation group was more obvious (P<0.05); compared with the control group, CD3+^{, CD4}+^{, CD4}+^/CD8+ in the observation group were significantly increased after treatment (P<0.05). Conclusion The effect of Icotinib hydrochloride combined with Gemcitabine and Carboplatin in the treatment of NSCLC patients is significant, which can effectively enhance the immune function of the body, inhibit the growth and metastasis of tumor cells, control the disease progression, and do not increase the toxic and side effects.