There have always been some attempts to control and prevent fires, as various fire incidents have occurred in a variety of buildings, with irreparable casualties and financial losses. One of the measures could be developing and enforcing new laws to delay flames in the buildings equipment. Aluminum composite Panel is one of the products used for building facades and it is very important in delaying the flames in buildings. This facade is composed of several layers, 75 of which is made of the flammable polyethylene layer. To ensure fire retardation of this facade, the middle layer, which is the polyethylene layer, has to be made fire-retardant by flame retardants. In this research, two kinds of flame retardant with poly(ethylene-co-vinyl acetate) as a coupling agent and flame retardatio aid were used to serve as flame retardant in the polyethylene layer, ultimately acting as the flame retardant of aluminum composite Panel. To this aim, the materials were first mixed at different percentages of the flame retardants and then the slow-burning polyethylene sheet was prepared. Finally, after preparing the specimens for different tests and performing mechanical and flammability tests at the same time, the best combination of flame retardants percentages was determined. The results of this research showed that by increasing magnesium hydroxide to polyethylene/poly(ethylene-co-vinyl acetate) matrix, the mechanical properties were weakened; tensile strength and elongation percentage were decreased as well. In this study, the composite filling point was observed at 55 wt% magnesium hydroxide using a three-point bending test; as a result, as the filler was increased, the mechanical properties were decreased sharply. With the increase of ammonium polyphosphate to the polyethylene poly (ethylene vinyl acetate)/ magnesium hydroxide composite, the elongation percentage was raised and the amount of flexural strength was decreased, leading to the improvement of the thermal and flame retarding properties. So, with increasing 10 wt% of ammonium polyphosphate to the composite, the value of the limiting oxygen index was raised; also, with a 5 wt% further increase of this material, the limiting oxygen index was raised by 2 percent; also, adding 15% by weight of ammonium polyphosphate to the composite will rank the composite in the vertical burn test and by increasing the weight by 5% more, the composite will get a better rating (V-1) in the vertical burn test. Concerning the mixing process, specimens prepared with a double screw extruder, in comparison to the internal mixer, due to better mixing and the sheets prepared by injection molding, as compared to hot pressing, owing to the higher pressure and less molding time, had better flammability and mechanical properties. Images obtained from scanning electron microscopy test also confirmed the lack of good dispersion in the specimens prepared with the internal mixer and the existence of bubbles in the specimens prepared with compression molding. Poly(ethylene-co-vinyl acetate) improved the flame retarding properties in addition to coupling properties; so, y increasing the amount of limiting oxygen index of polyethylene blend mixed with poly(ethylene-co-vinyl acetate) as much as one unit, as compared with pure polyethylene, the vertical burn was increased; also, in the ethylene without additive test, it was flaming 3 minutes 53 seconds later to the end of the clamp, as compared to polyethylene. Finally, the best weight percent composition was obtained in terms of both mechanical and thermal-flame retarding properties; also, regarding the applicability of this research and its economic aspect, the combination of 33.75% polyethylene / 11.25% poly(ethylene-co-vinyl acetate)/ 35% Magnesium hydroxide/ 20% ammonium polyphosphate can be suggested. This percent composition, in addition to the high limiting oxygen index and the best rating in vertical burn test, can have better mechanical and thermal properties than other compounds. Key words: polyethylene, flame retardant , oly(ethylene-co-vinyl acetate), aluminum composite panel, thermal stability, ammonium polyphosphate, magnesium hydroxide