Tubular structure system is one of the most suitable structural form of tall buildings. In this system, the responsibility of repelling lateral forces is on peripheral tubular bending frames with high stiffness. One of the most common issues of this system which affects the operation efficiency is shear lag phenomena. In this study, in order to improve the transformation of load between the columns and decreasing shear lag, the use of mid-story beam is considered in the openings of the tube frame and Also, the study of the number of openings required for the mid-story beam the rigidity parameter of the mid-story beam has been studied. For this purpose, ETABS software is used for 3D modeling of tall steel structures with different number of floors had been used and The values of its shear lag index, lateral displacement and stories drift ratio are investigated.The results of the study showed that the use of mid-story beams improved the lateral response of the structure and, on the other hand, led to a reduction in the shear lag index where by increasing the number of structural floors, using this system has more significant effect on the structural performance.