Pembelajaran Bahasa Indonesia dapat mengembangkan kemampuan berbahasa, baik lisan maupun tulisan. Kurangnya keefektifan pembelajaran menimbulkan kurangnya pemahaman siswa khususnya pada siswa yang kurang aktif, kurangnya minat dalam mengerjakan tugas dan berdampak pada nilai siswa dengan adanya permasalahan tersebut peneliti ingin mendeskripsikan peningkatan menulis teks eksplanasi siswa kelas XI SMA Hang Tuah Tarakan dengan menggunakan metode pembelajaran Inquiry Based Learning. Jenis Penelitian yaitu tindakan kelas (Classroom Action Research). Subjek penelitian memilih salah satu kelas yang memiliki kendala menulis teks eksplanasi. Desain penelitian yaitu perencanaan, pelaksanaan, pengamatan (Observasi), refleksi. Instrumen Penelitian yaitu Instrumen Pedoman Penilaian, Instrumen Tes Hasil Belajar Siswa, Lembar Observasi Pembelajaran. Teknik Pengumpulan Data Observasi, Tes, Dokumentasi. Teknik Analisis Data Teknik Analisis Data Kualitatif Teknik Analisis Data Kuantitatif, Indikator Keberhasilan Proses. Hasil peningkatan kemampuan menulis teks eksplanasi pada siklus I observasi guru mendapatkan skor 64 dengan skor rata-rata 32 terbilang cukup, observasi siswa mendapatkan skor 64 dengan skor rata-rata 32 yang terbilang cukup. Nilai KKM 75, 14 siswa mendapatkan nilai dibawah kkm terbilang tidak tuntas. Siklus II terdapat peningkatan observasi guru mendapatkan 82 skor rata-rata 41 yang terbilang baik, observasi siswa 81 skor rata-rata 40,5 yang tebilang baik. Dalam analisis nilai tugas pada siklus II terdapat peningkatan kemampuan menulis teks eksplanasi yaitu 23 Siklus I siswa tidak mengalami peningkatan dan siklus II mengalami peningkatan.

Indonesian language learning can develop language skills, both spoken and written. However, the ineffectiveness of teaching-learning process causes a lack of students understanding, especially when the students were less active or lack of interest in doing assignments, it will have an impact on their scores. Regarding the aforementioned problems, the researcher aimed at describing the students improvement in writing explanatory texts in class XI SMA Hang Tuah Tarakan using Inquiry Based Learning method. This type of rescarch was classroom action research. The research subject was chosen by determining a particular class witha problem of writing explanatory texts. The research design consisted of planning implementation, observation, and reflection. The research instruments were assessment guidelines, student learning outcomes test, learning observation sheets. Data collection techniques were observation, test, and documentation. Data analysis techniques used qualitative data analysis techniques, quantitative data analysis techniques, and indicators of success. In the first cycle, the results of teacher observation got a score of 64 with an average score of 32 which was classified as sufficient, student observation got a score of 64 with an average score of 32 which was classified as sufficient. The Minimum Mastery Criteria (KKM) Score was 75, 14 students got scores under the Minimum Mastery Criteria which was considered incomplete. In Cycle 1, there was an improvement in teacher observation achieving score 82 and the average score was 41 which was in good category. Student observation score was 81 with an average score of 40.5 which was classified as good. Considering the analysis result of the assignment scores in cycle 11, there was an improvement of the explanatory text wniting skills, namely 23 students who did not experience an improvement in Cycle I experienced an improvement in Cycle II.