To improve the quality of wheat noodles, this study added different proportions（0%, 2%, 4%, 6%, 8%） of soybean dietary fiber to wheat flour noodles, and measured their stretching properties, cooking properties, and glycemic index（GI）. The results showed that the addition of soybean dietary fiber made the tensile properties of noodles increase first and then decrease. The results of cooking characteristics showed that the water absorption rate, expansion rate and breaking rate increased with the increase of soybean dietary fiber, and the loss decreased first and then increased, which indicated that proper addition of soybean dietary fiber could optimize the quality characteristics of noodles. The tensile properties and cooking characteristics indicate that the addition amount is less than 4%. The GI value of cooked noodles was determined by compound enzyme method in vitro. It was proved that adding soybean dietary fiber could inhibit the hydrolysis of starch and reduce the GI value of mixed noodles.