Abstarct: Determination of the ultimate strength of casing due to its critical role in drilling and production phases is significantly important. The parameters involved in reduction the strength and collapse of casing can be divided into two categories: intrinsic and environmental parameters. Among these parameters diameter to thickness ratio, eccentricity, formation type, temperature and pore pressure are of the most important ones. In order to determine the ultimate strength of casing, empirical formula and numerical methods are commonly used. However, empirical methods are not able to provide reliable results due to lots of assumptions and neglecting some of the effective conditions causing casing to damage. That is why numerical methods are being found as an effective approach in determination of strength of the casing. In this study, to simulate ultimate strength of casing, and prediction of casing collapse, mechanical properties of formations were firstly estimated through utilizing of well logs data and used for modeling by nommercial ABAQUS software. Sensivity analysis was performed some parameters effective on casing strength. Results obtained from this 3D modeling indicated that stress anisotropy and diameter to thickness ratio are the most important parameters may cause casing to damage.