The investigators performed a multi-centered, randomized, double blinded, placebo-controlled, prospective clinical trial on the effect of YYJD, a chinese herbal medicine (CHM) formula combined with gefitinib in advanced pulmonary adenocarcinoma patients with activating EGFR mutation (exon19del or exon21L858R) that choose gefitinib as first-line or second line therapy. Patients are randomized into observational group (YYJD plus gefitinib),and control group (placebo plus gefitinib). The treatment should be continued until evidence of disease progression or unacceptable toxicity, and after that regular follow-up will be arranged. The primary efficacy assessments are: PFS (progression-free survival); Secondary efficacy assessments are: (1) OS (overall survival); (2) Objective response rate; (3) QOL (Functional Assessment of Cancer therapy-lung, FACT-L4.0 scales; Lung Cancer Symptom Scale, LCSS); (4) other efficacy assessments are: 1) TCM symptoms changes; 2) Toxicity, side effects and security of the treatments will be assessed at the same time. The investigators plan to enroll 198 cases in 3 years (99 cases for gefitinib, 99 cases for gefitinib plus YYJD), expecting that combination therapy has a better efficacy on prolonging PFS, overall survival, improving quality of life(QOL). Therefore the study can provide evidences for optimizing and promoting the efficacy of gefitinib.