In recent years, extensive studies have been conducted for the development of additive manufacturing technology and in particular Selective Laser Sintering (SLS) process. Although the findings suggest significant advances in this regard, there are Still, challenges such as the limited range of materials to be processed, the weakness of mechanical properties of parts compared to the components produced in conventional methods and the low repeatability of the properties. Among the influential parameters in the SLS process, the distribution of surface temperature of the powder bed surface is probably the most important factor in the manufacturing of components with the same and repeatable properties in the process. The purpose of this study was to optimize the pre-heating system in the SLS powder bed and to control the temperature distribution of building platform in order to achieve a uniform temperature distribution at the surface the bed, as well as to improve the temperature control system to reduce the build time. In order to mimics the real chamber of SLS system. Firstly, a similar test chamber was designed and manufactured. The design of the fabricated test chamber allowed to examine various type of heaters for heating up the powder surface within the chamber as well as their location and layout. After that, several experiments were designed and carried out to find out the proper resistive heaters type, their optimum power, and their hight. These findings were implemented within the chamber of SLS system. The result of measuring the temperature powder bed surface of SLS system after modification using a thermal camera revealed that the temperature differences within the powder bed surface decreased to less than 6 o C. The temperature difference on the powder surface was about 20 o C before the modification. In order to investigate the performance of SLS system after modification series of test parts from Polyamid12 (PA12) and Polystyrene (PS) material, with wide window processing, the ultimate tensile strength and the fracture elongation of test samples were found to be 46±2 MPa and 23±3 % respectively which were quite superior propertis compared to the literature reports. On the other hand, for PS material with narrower process window, 10 o C, it was possible to produce intricate parts sucssessfuly. Besides the ultimate tesile strength and elongation of the tested parts were found to be 17.67±0.46 MPa and 2.75±0.28 % respectively, reaviling the capability of the implemented modifications. Keywords: Additive Manufacturing, Selective laser sintering, SLS, Heater, Optimization, Processing Window, Polyamide12, Polystyrene