Abstract: Gene targeting is a molecular technique that has been exited since 1980’. It can be applied in researching the gene function, removing gene silence and gene therapy. Gene targeting is an important method in functional genetics. Now, it has been successfully used in yeast and mouse embryonic stem cells(ES). But in plants it has been limited because of lower recombination frequency. The recombination frequency in Physcomitrella patens is high, so it is expected to be a new molecular biological model plant.