<![CDATA[Based on observations at Muhammadiyah Junior High School in Pekalongan, Lampung Timur shows that critical thinking skill of students is still low. This research was intended to increase the students activity and critical thinking skill through using discovery method. The design of the research was pretest-posttest non equivalent group design. The sample of this research were the students of VIIa and VIIc class which was chosen by purposive sampling. The qualitative data obtained from the observation sheet of learning activities of students were analyzed descriptive. The quantitative data obtained from the average value of pretest, posttest, and N-gain that were analyzed by the U test. The results showed that students activities in experiment class improved. The critical thinking skill of students also improved with average pretest score 49,86; posttest 76,64 and N-gain 48,52. Thus, it can be concluded that increasing of learning activities and critical thinking skill of students is influenced significan by using discovery method.Berdasarkan observasi di SMP Muhammadiyah Pekalongan, Lampung Timur, diketahui kemampuan berpikir kritis siswa masih rendah. Penelitian ini bertujuan untuk mengetahui peningkatan aktivitas belajar dan kemampuan berpikir kritis siswa melalui metode diskoveri. Desain penelitian ini adalah desain pretes-postes kelompok tidak ekuivalen. Sampel penelitian adalah siswa kelas VIIa dan VIIc yang dipilih secara purposive sampling. Data kualitatif diperoleh dari lembar observasi aktivitas belajar siswa yang dianalisis secara deskriptif. Data kuantitatif diperoleh dari rata-rata nilai pretes, postes, dan N-gain yang dianalisis menggunakan uji U. Hasil penelitian menunjukkan bahwa aktivitas siswa pada kelas eksperimen mengalami peningkatan. Kemampuan berpikir kritis siswa juga mengalami peningkatan, dengan rata-rata pretes sebesar 49,86; postes sebesar 76,44 dan N-gain sebesar 48,52. Dengan demikian, pembelajaran menggunakan metode diskoveri berpengaruh signifikan dalam meningkatkan aktivitas belajar dan kemampuan berpikir kritis siswa.Kata kunci : aktivitas belajar, ciri-ciri makhluk hidup, kemampuan berpikir kritis, metode diskoveri ]]>
