The quality requirement of rebars for construction industry has increased interest in improving mechanical properties of reinforcing bars used for building concrete structures. The variation of mechanical properties of rebars manufactured from metallic scraps by Ethiopian iron and steel rolling mill factory has been investigated in this research. The purpose of this work was to improve mechanical properties of rebars by upgrading chemical compositions making use of Taguchi optimization approach and minimizing product defects by enhancing process parameters in continuous casting and hot rolling processes using numerical simulation methods. The study was carried out on commonly used rebars samples including 10, 12, 14 and 16 millimeters in diameter. In order to check quality of rebar and its conformity with standard, experimental works on mechanical tests like tensile and hardness tests using Universal tensile testing and Rockwell hardness testing machines respectively were conducted. Chemical composition tests were also conducted using Atomic Emission Spectrometer (AES) with model METAVISION-108. During conformity test, yield strength of 75% of rebars was deviated from standard value specified in Ethiopian standard. From present study, it was observed that for product sample taken, the chemical composition and tensile strength do not comply with Ethiopian standard. Defects on product quality were caused due to composition of alloying Elements and parameters of continuous casting, hot rolling and heat treatment processes. At the end of the study, the result showed that the Yield strength of bar has been improved in 80.78%(268.997Mpa).Thus the Yield strength of bar has been improved by controlling chemical composition of steel and production process parameters at optimum level using Taguchi Method and a simulation-driven approach using a commercial packages (Ansys 15.0 and Abaqus 6.1.4), based on finite element methods.