In order to understand the behavior of ligninolytic enzyme production by white rot fungi Phanerochaetechrysosporium, study on time courses and a mathematical model for the production of lignin peroxidase (LiP) andmanganese peroxidase (MnP) of the fungi was undertaken. Based on the Monod-Jacob operon model, the ligninolyticenzyme would be synthesized in the absence of a related repressor. The repressor is assumed to be active in thepresence of ammonia nitrogen, and as combined as co-repressor, it causes the inhibition of enzyme synthesis. Themodel can explain the mechanism of extracellular ligninolytic enzyme production by white rot fungi. The results,as predicted by the model, correspond closely to those observed in experimental studies. In addition, some lightis also shed on unmeasured variables, such as the concentrations of repressor and mRNA that are related to theenzyme synthesis.