Abstract: The Rho GTPases are major members of the Ras superfamily proteins. It is well known that there are several Rho GTPase interacting each other and regulating many signal transduction pathways in eukaryotes. To study the relationship of 7 putative Rho-GPTases in the Magnaporthe grisea genonme, RT-PCR was used to analyze the Rho GTPase gene expression patterns in different MgCdc42 and MgRho3 mutants. It was found that MgCdc42 positively controlled the expressions of MgRho1, MgRho2 and MgRhoX; negatively regulated MgRac1 and MgRho4; however MgRho3 positively regulated the expressions of MgRho1 and MgRho2, but negatively controlled MgRho4 and MgRac1. And the relationship between MgRho3 and MgCdc42 was complicated. The result will facilitate to understand the functional relationship of different GTPases in M.grisea and other filamentous fungi.