Using the melt impregnation device developed at our laboratory, long glass fibers reinforced thermoplastic polyurethane elastomer (TPU) and polylactic acid (PLA) composites were produced, using styrene-acrylonitrile grafted methyl acrylic glycidyl ester (SAG) as compatibilizer, thermoplastic polyurethane elastomer as toughening agent and polylactic acid (PLA) as matrix resin. And effects of compatibilizer content on performance of long glass fibers reinforced TPU/PLA composites were studied. The results demonstrate that the addition of styrene-acrylonitrile grafted methyl acrylic glycidyl ester (SAG) improves the compatibility of long glass fibers reinforced TPU/PLA composites. The tensile strength, notch impact strength, bending strength and modulus, and storage modulus of long glass fibers reinforced polystyrene composites firstly increase and then decrease with increasing styrene-acrylonitrile grafted methyl acrylic glycidyl ester content; The tanδ of long glass fibers reinforced polystyrene composites firstly decrease and then increase with increasing the styrene-acrylonitrile grafted methyl acrylic glycidyl ester content; SEM morphology analysis of composites shows that the addition of styrene-acrylonitrile grafting methyl acrylic glycidyl ester compatilizer increases the interface strength between glass fiber and matrix resin of composite materials, and glass fibers are coated with the matrix resins. When the SAG content is 6%, the tensile strength, bending strength and modulus, notched impact strength of long glass fiber reinforced TPU/PLA composites are optimal.