The purpose of this research is; to analyze the differences in the increase in critical thinking skills, science process skills, and self-efficacy between the application of assisted inquiry learning models PhET simulation and conventional methods assisted by question and answer students of class XI IPA 1 West Malaka. The research method used was quasi-experimental. The research subjects were students of class XI IPA of SMAN 1 West Malaka in the 2018/2019 academic year. Data collection techniques consisted of observations, Critical thinking and Science Procesess tests, and selfefficacy questionnaires. The data obtained in this study were analyzed using descriptive and inferential statistics. Based on the analysis of the N-gain test, the average N-gain was obtained to see the increase in Science Procesess and self-efficacy depending on the medium category, and N-gain in the high category. The t test paired with a simple Critical thinking, Science Procesess and Self Efficacy test for the posttest and the experimental class pretest had a sig value. 0,000 <0,05 tested the increase, while the independent sample t-test for Critical thinking and Science Procesess for the posttest control class and experimental class had a sig value. 0.048 <0.05 and 0,000 < 0,05, there is a difference in Critical thinking and Science Procesess between the application of the guided inquiry method assisted by PhET simulation and the lecture method assisted by question and answer, while the independent sample t-test for Self efficacy the posttest control class and experimental class had a sig value. 0.407> 0.05, there was no difference in increase in self-efficacy between the application of the guided inquiry method assisted by the PhET simulation and the lecture method assisted by question and answer. / Tujuan dalam penelitian ini adalah; untuk menganalisis perbedaan peningkatan kemampuan berpikir kritis, keterampilan proses sains, dan self-efficacy antara penerapan model pembelajaran guided inquiry berbantuan Simulasi PhET dan metode konvensional berbantuan tanya jawab siswa kelas XI IPA SMAN 1 Malaka Barat. Metode penelitian yang digunakan adalah kuasi eksperimen. Subyek penelitian adalah siswa kelas XI IPA SMAN 1 Malaka Barat tahun ajaran 2018/2019.Teknik pengumpulan data berupa observasi, Tes KBK, Tes KPS, dan angket self-efficacy. Data yang diperoleh dalam penelitian ini dianalisis mengunakan statistik deskriptif dan inferensial. Berdasarkan analisis uji N-gain diperoleh bahwa rata-rata N-gain untuk melihat peningkatan KBK dan self-efficacy berada pada kategori sedang, dan N-gain KPS berada dalam kategori tinggi. Uji t paired simple test KBK, KPS dan SE untuk posttest dan pretest kelas eksperimen memiliki nilai sig. 0,000 < 0,05 mengalami peningkatan, sedangkan uji-t independent samples test KBK dan KPS untuk posttest kelas kontrol dan kelas eksperimen memiliki nilai sig. 0,048 < 0,05 dan 0,000 < 0,05 maka ada perbedaan peningkatan KBK dan KPS antara penerapan metode inkuiri terbimbing berbantuan simulasi PhET dan metode ceramah berbantuan tanya jawab, sedangkan sedangkan uji-t independent samples test self-efficacy untuk posttest kelas kontrol dan kelas eksperimen memiliki nilai sig. 0,407 > 0,05 maka tidak ada perbedaan peningkatan self-efficacy antara penerapan metode inkuiri terbimbing berbantuan simulasi PhET dan metode ceramah berbantuan tanya jawab.