Three series composites of polyurethanes reinforced with glass fibers with different length were prepared in 2 steps. Urethane prepolymers were synthesized of diisocyanate and a polyester polyol in the first step. In second step, the short glass fibers (4.5 mm) and chain extender (butanediol, 1,4-diazabicyclo[2.2.2]octane) were added to the sample of prepolymer or the prepolymer was added in 2 wt. parts into the steel form filled with axially and biaxially aligned glass fibers. The composite with the long glass fibers (140 mm) aligned blaxially showed the max. tensile strength. The composite with glass fibers axially aligned showed the max. Schob elasticity.