Abstract: In order to describe the electromagnetic properties of the double negative material, using improved parameterretrieval method based on S parameters to retrieve the electromagnetic parameters of this material, the most prominent feature ofthis method is to retrieve the parameters of the material is use the intrinsic link of the parameters when to retrieve, not the usual ofusing S parameters to retrieve the parameters independently, thus ensuring the consistency of the retrieval results. A millimeterwave double negative material with the SRRs and rods has been designed based on the above retrieval method, and retrieved itsparameters. To test the feasibility of this improved method, using this method to retrieve X-band parameters of double negative materials, and through the comparison with the related documents retrieval results find that they are in agreement basically, whichverifies the feasibility of this retrieval method in other bands.