The aim of this study was to detect the epidermal growth factor receptor (EGFR) gene type at pre- and postchemotherapy to evaluate the impact of platinum-based chemotherapy on EGFR gene mutations and provide a theoretical foundation for clinical treatment. Around 40 serum DNA samples were collected from advanced nonsmall cell lung cancer patients who received platinum-based chemotherapy as first-line treatment in our hospital from August 1, 2014 to June 1, 2015. The EGFR gene exons 19 and 21 were amplified by polymerase chain reaction (PCR) and detected by direct sequencing. The outcomes were analyzed with SPSS 17.0. Of 40 patients, 38 were included in the analysis. An EGFR gene mutation was detected in 17 cases (44.7%) at prechemotherapy compared with 19 cases (50.0%) at postchemotherapy. The EGFR gene mutation differences were not statistically significantly (P = .165) during pre- and postchemotherapy. The EGFR gene type was consistent in 26 cases (68.4%). Among the 12 discordant cases, 5 cases changed from mutant type to wild type, while 7 cases changed from wild type to mutant type. EGFR mutation positive patients had a disease control rate (DCR) of 88.2% (15/17), whereas it was only 57.1% in EGFR mutation negative patients, which was statistically significant (P = 0.01) indicating a better curative effect in EGFR mutation positive patients. Platinum-based chemotherapy may change the serum EGFR gene type in advanced lung adenocarcinoma.