Abstarct: The Moment Resistant frxame (MRF) has a large ductility capacity; but this feature has defects. When huge loads due to earthquake applied to the structure and large displacement occurred, extreme damages applied to structural and nonstructural elements. On the other hand, Concentrically Braced frxames (CBFs) have a high elastic stiffness which prevent large drifts. The ability of CBFs to dissipate energy result in a good performance against lateral loads. So, combined of MRF and CBFs can be as dual system for upgrading or a retrofitting strategy after an earthquake. Incorrect implementation in brace connection and buckling of bracing elements are defects of CBFs. An idea to eliminate this problem is to utilize steel wire ropes. Having small area sections, light weights, high tensile strength and provide safety against buckling and having high resistance against corrosion, erosion and fatigue are advantages of steel wire ropes. Pre-stressing is a good method to exploit maximum tensile strength and both cables act as tension elements. This thesis focused on behavior factor, weight and drift of Steel Moment Resistant frxame Braced with Pre-stress Steel Cables (SMRFBPSCs). So 3D SMRFBPSCs were simulated in buildings with 3, 6 and 12 story in SAP2000. The cables were at 2 arrangement: 1. X shape and single-brace (bracing at each story); 2. X shape and mega brace (bracing 3 story with one pair cable). The cables were pre-stressed. The analysis method was nonlinear static analysis (pushover) and design structural elements accomplished according to limit states method. Earthquake loading conducted by 2800 Iran code (fourth edition). In calculating R (behavior factor), two method were accomplished in this study; A conventional method (R1) and a method offered in this study (Ru). In the offered method, earthquake coefficient reformed at each step with from R recent step; try and error process with consideration conditions utilized to convergent to an amount of number. Results designate in all models, Ru less than corresponding R1. The change pattern of Ru versus model change, is similar to R1. Applying pre-stress to cables and increase amount of them, R1 and Ru are increase. Finally in non-prestress cable R1 vary from 4.54 to 6.25 and Ru vary from 3.88 to 5.3; for pre-stressing cable R1 vary from 4.66 to 6.9 and Ru vary from 4.03 to 6.99. The results of simulation shows by adding cables to MRFs; weight of short (3st) and partly short (6st) constructions are decreased but weight of medium structure (12st) decreased at first, then increased. In other words, increasing cable diameter is conduce to weight decrease. Single arrangement had more efficiency in decreasing weight than mega arrangement. Despite partly short construction mega arrangement had better results. Therefor arrangement of cables and height of structure are correlative parameters. Generally, adding cable to short structure had more effect in decreasing the weight of them than medium structure. Pre-stressing cables and increase amount of them cause weight of structure to become lighter than non-prestress cables. Finally, impression of drift change were evaluated in this study. Adding cable to MRF cause drift to decrease noticeably and for single arrangement decreasing was more than mega arrangement; therefor mega arrangement is more desirable because of more ductility. Moreover increasing in pre-stressing had not noticeably impression on drift. Generally, SMRFBPSC had more impression on drift of short construction toward medium structure.