In this research three groups of polymer blends have been prepared First groupincluded (Polystyrene (PS): Low density polyethylene (LDPE))While the Second group(included Polystyrene (PS): Polypropylene (PP)) and Third groups include (Polystyrene (PS): Poly methel methacrylate(PMMA)) are prepared in different ratios by melt blending technique which was carried out using a double screw extruder. The tensile, flexural, impact and hardness test are used to study mechanical propertiesof polymer blends. The results from this work show that the impact properties for blends system increases with increases each of (LDPE, PP and PMMA) content in polymer blends of (PS: LDPE), (PS: PP) and (PS: PMMA). The elongation property increases with increases LDPE and PP but decreases when adding PMMA in polymer blend.