Abstract: The blue egg is caused by a dominant mutation (O) and preliminary assigned to the interval of 1.8 Mb from 67.29, 6.991-69.1, 40.571 bp on chromosome 1. In order to refine the localization of the O gene, linkage analysis was performed between 6 markers in the mapping interval and the O locus using 149 F2 offspring from an intercross between DongXiang blue-shelled and DongXiang brown-shelled chickens.