This study aimed at investigating the effect of computer based simulation in physics achievement and spatial thinking among grade eleven female students. The sample of the study consisted of (64) female students enrolled in grade eleven in Basic Education school in Al- Batina North Region. The sample was split up into two groups: control group (N=32), and was taught by the conventional method and the experimental group (N=32), and was taught using the computer based simulation method. To answer the research questions, two tests were administered. While, the first test was a physics test, consisting of (22) subjective and essay questions, the second was a spatial thinking test, and was codified and applied for Oman. Validity of both tests were checked through a panel of judges whereas, the reliabilities were carried out by consistency type of reliability using Alfa cronbach method, giving value of (0.81) and (0.87) respectively. Such reliability values are consented for the purpose of the study. The results revealed the followings: - There are significant differences between the experimental and the control group in physics achievement test in favor of the experimental group. - There are no significant differences between the two groups in the spatial thinking test. - There is an interaction between the teaching technique (simulation) and the academic level in favor of students with good achievement. Eventually, the researcher proposed several recommendations for science educators; such as: training science teachers and supervisors necessary techniques to address simulation in their teaching. The researcher also suggests tackling more research in such area.