Abstract: The suspended culture of fungus is a quite complex biochemical process.The modelling offungus fermentation is necessary for optimizing this process. However,there are some undetermined factorsduring the fermentation process,such as variety of microorganism, changes in facilit and circumstances,Some of these would cause stochastic noises disturbing the bioprocess. In this paper an extended Kalman-fil-tering was used to improve the precision of the simulation of mathematical model.The results of calculationshowed that the precision of the estimation of state variables could be ameliorated by using this filter.