In this research,It aims to develop polycarbonate (PC) and acrylonitrile-styrene-acrylate (ASA) blends for high impact resistant products for outdoor applications. PC/ASA were blended at various grades of ASA (3 grades at impact strength and melt flow index different, i.e. ASA-997, ASA-978 and ASA-777)and compositions (i.e. containing 50- 90 wt% of PC) to investigate the effect of ASA grades and blend compositions on phycical, mechanical and thermal properties. The storage modulus at room temperature of all PC/ASA blends from dynamic mechanical analysis steadily increased with an increasing of PC contents. Moreover, PC/ASA-997 showed the highest modulus from the other PC/ASA blends system, i.e. PC/ASA-978 and PC/ASA-777. Glass transition temperatures (Tg) of all PC/ASA blends revealed that Tg of both PC-rich phase and ASA-rich phase slightly shifted towards each other with increasing amount of the PC. It showed that, PC/ASA blend can be classified as a partially miscible. Furthermore, notched Izod impact strength from impact tester of all PC/ASA blends clearly increased with an increasing PC contents in these polymer blends that PC/ASA-997 blend was also shown the highest impact strength. Whereas, PC/ASA-777 showed the highest melt flow index. The melt flow index of all PC/ASA blends distinctly incresed with an increasing amout of ASA in the blend. In particular, ASA was found to significantly improve the color and the impact strength retention of pure PC. From result of QUV exposure, a time period up to 3 week in QUV, the impact strength retention after weathering test increased with an increasing ASA content from 77% to 91% for 10 wt% to 50 wt% of ASA content, respectively. These evidences indicated that ASA can improve weatherability of these blends.