The objective of this research was to find out the effectiveness of POE Model on buffer solution material in increasing students elaboration thinking ability. The research method was using quasi experiment with the non equivalent (pretest-posttest) control group design. By using purposive sampling technique, the samples of this research were the second grade science 1 and the second grade science 4 of SMA Negeri 15 Bandar Lampung in academic year 2015/2016. The result of the data showed that the score average n-Gain of experiment class was 0.64 and the control class was 0.28. Based on the average n-Gain of experiment and control class, it can be concluded that POE model was effective in increasing students elaboration thinking ability towards buffer solution material.Penelitian ini bertujuan untuk mendeskripsikan efektivitas model POE dalam meningkatkan kemampuan berpikir elaborasi siswa pada materi larutan penyangga. Metode penelitian menggunakan kuasi eksperimen tipe non equivalent (pretest-posttest) control group design. Dengan menggunakan purposive sampling, kelas XI IPA 1 dan XI IPA 4 di SMA Negeri 15 Bandar Lampung tahun pelajaran 2015/2016 terpilih sebagai sampel penelitian. Hasil penelitian diperoleh rata-rata nilai n-Gain kelas eksperimen yaitu 0,64 dan kelas kontrol yaitu 0,28. Berdasarkan rata-rata nilai n-Gain kelas eksperimen dan kontrol, dapat disimpulkan bahwa model POE efektif dalam meningkatkan kemampuan berpikir elaborasi siswa pada materi larutan penyangga.Kata kunci: berpikir elaborasi, efektivitas, POE