Abstract: [Objective] We established a genetic transformation system for Penicillium brevicompactum to produce mycophenolic acid.[Methods]We developed protoplast transformation methods mediated by Polyethylene glycol,using phleomycin resistance gene (Sh ble) as a dominant selection marker.[Result]The frequency of transformation was up to 2-3 transformants per μg DNA; analysis of the transformants by PCR showed that the foreign DNA had been integrated into the host genome.The transformants retained stable after generation.[Conclusion]The establishment of the genetic transformation system of Penicillium brevicompactum could serve as the basis for the research of molecular biology and the breeding of gene engineering of the fungus.