Concrete precast segments are predicated to those which manufactured in non-original site and then, install on the original site. Precasting has many advantages such as accelatering in production, better quality and reducing in overall costs. Although it is necessary to not forget about two main disadvantages of precasting which are traortation of segments and their joints. In fact, the most critical particle of these structures are their joints that caused important damages under lateral loads. Of course, with suitable design and correct construction of these joints, precast system operation would be fair; But in respect to few researches about this subject so far, lack of code criterias and also difficult construction of these joints, seems to be a little difficult. A solution to this problem, is using the prestress system in precast walls instead of several joints, might be convenient. So in this research, behavior of post-tensioned precast walls has been studied. Purposes for this study are the investigation on post-tensioned precast concrete shear walls seismic behavior and their performance comparison with similar monotonic ones. For this, finite element method and non-linear analysis via ABAQUS software modeling have been utilized. Accordingly, several concrete shear walls in 4, 6, 8 12 floors have been designed and modeled via ABAQUS software at two conditions of monotonic and post-tensioned precast, and then applied under lateral load. For connection of precast wall panels, dry-pack has been used. In addition, strength, ductility, energy absorption and cracking pattern are compared between two systems of monotonic and post-tensioned precast conditions. Modeling and numerical analysis results show that post-tensioned precast shear walls have higher strength in comparison to monotonic ones. And from point of view of ultimate displacement, there is no significant difference between the different walls. using post- tensioned system coused obviously reduction in produced cracks in monotonic walls and also, eliminates the major defect of precast shear walls by using dry-packs. Keywords : Precast concrete shear walls, Post-tensioning, Ultimate strength, Ductility, Energy absorption