Abstract: The present invention relates to a genomic DNA library substantially maintaining copy numbers of a set of genes or the sequences on a genome, an abundance ratio of the set of genes or sequences on the genome, and the polymorphic patterns substantially identical to that of the genomic DNA. The present invention also relates to a method of producing the above genomic DNA library. The genomic DNA library of the present invention is useful in analysis of genetic polymorphism; genetic diagnosis of a disease; preparation of DNA arrays; preparation of samples for searching open reading frames in analysis such as genome analysis; preservation of genes of endangered organisms; gene specimens; mutation analysis; nucleotide sequence analysis; analysis by hybridization methods such as Southern blot hybridization method, dot blot hybridization method, Northern blot hybridization method, macroarray hybridization methods using membrane and the like, or DNA microarray hybridization method.