Penelitian ini meneliti: 1) adakah perbedaan signifikan atas peningkatan kemampuan menulis mahasiswa yang menggunakan strategi self-editing – peer review dan peer review - self-editing; 2) adakah perbedaan signifikan atas peningkatan kemampuan menulis mahasiswa berdasaran grup proficiency yang berbeda di tiap kelas , dan 3) aspek menulis yang meningkat signifikan di kedua kelas. Subjek penelitian adalah mahasiswa IBI Darmajaya, Lampung. Penelitian menggunakan pendekatan kuantitatif. Instrumen penelitian: tes menulis dan Nelson English Language Proficiency Test (NELT). Hasil penelitian:1) ada perbedaan signifikan pada kemampuan menulis mahasiswa yang menerapkan strategi self-editing – peer review dan peer review -self-editing; 2) ada perbedaan sigifikan pada kemampuan menulis mahasiswa di grup heterogen di kedua kelas; 3) tata bahasa adalah aspek menulis yang meningkat paling signifikan. Self-editing dan peer review dapat meningkatkan kemampuan menulis mahasiswa, dan membalik urutan teknik mengedit dapat meningkatkankemampuan menulis mahasiswa secara berbeda.This research investigated: (1) was there a statistically significant difference of students’ writing improvement between the students treated with self-editing - peer review and peer review - self-editing; (2) was there a statistically significant difference of students’ writing improvement in different groups of proficiency of both classes; and (3) the aspect of writing significantly improved in both classes. The subject of this research was the students of IBI Darmajaya, Lampung. This research used quantitative approach. The instruments were writing test and Nelson English Language Proficiency Test (NELT). The result shows that 1) there was a significant difference of students’ writing improvement between Class A and Class B; 2) there was a statistically significant difference of students’ writing improvement in heterogeneous groups in both classes; 3) it was language use, a writing aspect mostly improved. Self-editing and peer review can help students to improve their writing. Besides, it is inferred that reversing the order of editingstages does affect students’ writing improvement differently.Keywords: Peer review, proficiency level, self-editing, writing improvement.