The aim of this study was to investigate the extent inclusion of the American National Science Education Content Standards (NSES) in the Omani physics content of science textbooks for grades (9-12). The Sample of the study consisted of all physics content in science textbooks of grades (9-12) in basic education in Oman. For the purpose of the study, a content analysis tool was developed. The validity of the tool conducted by asking a panel of experts to give their comments, and the reliability was calculated using Kappa Coefficient of categorical reliability giving value of 0.90 between one analyst and the researcher for a sample of one unit, which was selected randomly from the sample studied. The data was analyzed statistically and the results demonstrated that the physics contents in the science textbooks for the grades nine to twelve included the standards in the following order: First, the Unifying Concepts and Processes Standard in percentage of (34.98%). Second physical Science Standard in percentage of (16.42%). Third Science as Inquiry Standard in percentage of (15.02%). Fourth History and Nature of Science standards in percentage of (12.39%). Fifth Science and Technology standard in percentage of (10.69%). It was a clear negligible for the Science in Personal and Social Perspectives Science Standard and Earth and Space Science Standard, where settled in the final order in the percentage of (8.70%) & (1.80%), respectively, Finally, the study proposed some recommendations such as giving more attention to the American National Science Education Content Standards when developing physics content science curriculum, and building standards for all school subject and adapting the standards philosophy in the educational system. The study also recommended conducting more research in the field of analyzing more science textbooks in the same area for other classes.