The investigators performed a multi-centered, randomized, double blinded, placebo-controlled, prospective clinical trial on the effect of Yiqi-yangyin-jiedu decoction (YYJD), a chinese herbal medicine (CHM) formula combined with gefitinib to prolong the progression free survival (PFS) of advanced pulmonary adenocarcinoma patients with activating EGFR mutation (exon19del or exon21L858R). 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).