Abstract: Oyster mushrooms（Pleurotus）are important groups of commercially cultivated edible mushrooms worldwide. The identification of Pleurotus species is fundamental for correct identification of the individuals and exploiting their full potential in food industry. It’s very hard to identify varieties of them exactly since their shapes differ very much， which is influenced by their environments. In this study， it’s the first time to analyze genetic diversity of fungi using COXIII gene as molecular marker. We got 13 COXIII partial gene sequences of Pleurotus. Based on them， the 2D-clustering diagram and phylogenetic trees were built to research genetic relationship of Pleurotus. The results showed that the phylogenetic relation between any two of P. citrinopileatus， P. salmoneostramineus， P. abalonus and other Pleurotus strains（as a group）was distant； the relationship was very close between P. ferulae Lenzi and P. nebrodensis； P. ostreatus， P. ferulae and P. eryngii form a subgroup. The result， together with other researchers’ job and evidence of morphology， implied that COXIII gene was suitable for the analysis of genetic diversity of Pleurotus.