In this work prepared and study a polymer composite, where use polyester resin with asbestos fiber ratio (5%, 10% and 15%). First study effect of changing reinforcement percentage by asbestos fiber on coefficient thermal conductivity (k) of polymer composite. Result show decrease in the coefficient thermal conductivity (k) of composite materials with increase of weight percentage of asbestos fiber. Second, study effect of it above reinforcement ratio on the some of mechanical properties (Impact, tensile, fracture and hardness) for polymer composite. The result indicate increase value of mechanical properties with increase weight percentage of asbestos fiber. The impact strength was (2.7 kj/m2) for pure resin where reach to maximum value (7.83 kj/m2) at 15wt% of fiber .Hardness and tensile reach to maximum value at 15% weight percentage for asbestos fiber. The result illustrate improvement mechanical properties after reinforcing by asbestos fiber and these properties rises with increased in reinforcement percentage.