Objective To study the expression of serum IL-12 and IL-10 in lung cancer mice with spleen Qi deficiency syndrome and the effect of modified Huangqi Jianzhong decoction. Methods Using bitter and cold， diarrhea， weary， dieting methods of modeling， after the establishment of mice spleen Qi deficiency syndrome and Lewis lung cancer model， according to the experimental design to process mice of each group. After modeling modified Huangqi Jianzhong decoction gavage， the mice were killed by taken off the cervical spine， and serum was collected. Tumor weight per mouse was noted， ELISA method was used to detect serum IL-12 and IL-10 in lung cancer mice. Results “Spleen Qi Deficiency” can significantly affect the expression of IL-12 and IL-10 in serum of lung cancer mice； Modified Huangqi Jianzhong decoction can down regulate the expression of IL-10， and increase the expression of IL-12（P<0.05） in serum of lung cancer mice. Conclusion “Spleen Qi Deficiency” can lead to abnormal drift of Th cells in lung cancer mice， which may be a expression disorder of immune regulation disorder of lung cancer mice， and Modified Huangqi Jianzhong decoction can help to restore immune regulation of lung cancer mice.