This study aimed to investigate the effect of using the debate strategy to teach Socio Scientific Issues (SSI) in developing critical thinking and the perceptions of eleventh grade students about sustainable development in the Sultanate of Oman. The study followed the quasi-experimental approach, where the study sample consisted of (51) students from the eleventh grade in a school in the Governorate of Muscat. They were divided into two groups: an experimental consisted of (22) students, and control consisted of (29) students, and the duration of the study was (6) weeks during the second semester of the academic year 2019/2020. To achieve the goals of the study, the (Watson & Glaser, 1999) critical thinking test was used in three skills, which has reliability of (0.92). A scale of perceptions on sustainable development has been built, which consists of (24 ) items distributed in three areas, and its reliability coefficient reached (0.71). A teacher's guide was prepared with the students 'worksheets, where the validity of the study material was verified by presenting it to a panel of reviewers. The results of the study showed that there was no statistically significant difference at the level of (α≤0.05) between the mean scores of the two groups in the post-critical thinking test. The results also indicated there is a statistical difference at the level of (α≤0.05) between the mean scores of the two groups in the post scale of perceptions about sustainable development for the benefit of the experimental group. In light of the previous results, the study recommended that science curricula should include social and scientific issues and sustainable development issues, use strategies and methods to develop critical thinking, and conduct more research on the use of the debate to discuss socio-scientific issues with other variables.