This research includes an experimental study for the manufacture of a composite material based on polymer (unsaturated polyester), reinforced with random fiberglass at different weight fractions. By suite, it has been studied some mechanical properties of the models manufactured, to determine the effect of glass fiber content on the tensile strength, hardness and impact resistance. This study has shown that the best results were for samples reinforced by 40% fiberglass, where the tensile strength increased about 70%, hardness up to 30%, and impact resistance about 43%. It will be observed that the mechanical properties decrease clearly at 60% of weight fraction of fiberglass. This fact can be related to the quantity of unsaturated polyester become inadequate for recharge of the fibers, which leads to weakness in the forces bonding in composite materials.