Abstract: Americal scientists Mario R Capecchi, Oliver Smithies and British scientist Martin J Evans are` jointly awarded the 2007 Nobel Laureates in Physiology or Medicine on 8 october 2007 for their discoveries of "principles for introducing specific gene modifications in mice by the use of embryonic stem cells" （technology of gene targeting）. Gene targeting allows scientists to establish the roles of individual genes in health and disease. This article will introduce the techonology of “gene targeting”.