Styrenic copolymers such as high impact polystyrene (HIPS) and poly (acrylonitrile-co-butadiene-co-styrene) (ABS) are playing a very important part in the electronics industry. They are used for the production of TV housings, computers and office equipment. As they burn easily, they have become a real threat to users and it has been necessary to improve significantly their flame retardancy. ABS materials without flame retardant are easily burned with a luminous yellow flame, smoking strongly and continue to burn after removal of the ignition source. For applications requiring higher degrees of flame retardancy, ABS grades have been developed based on alloys with PVC polymer blends or through an additive approach using halogen in combination with antimony oxide. In this work, to improve of mechanical and flammability properties of ABS we used graft-ABS, Unplasticised- poly (vinyl chloride) (UPVC) powders and poly (styrene-co-acrylonitrile) (SAN) powder as a compatibilizer. Three types of suspension grade of UPVC are utilized because of their good flammability resistance and good compatibility with SAN. Appropriate heat-stabilizer and internal lubricant without adding any filler are used. Samples of ABS/UPVC blend were produced with weight ratio 90/10, 80/20, 70/30 and 60/40 by using co-current twine extruder. Glass transition temperatures, compatibility, and thermal stability were determined by using a differential scanning calorimeter (DSC). The mechanical properties were characterized by using universal testing machine. To analyze of flame retardancy standard test of UL 94 was applied. Final results show the improvement of mechanical and flame retardency properties for ABS/UPVC blends.