Abstract: Malt was the major raw material used for beer brewing, its surface had different microorganism. Malt infected by the mould could induce the increase of β-glucan, soluble nitrogen and viscosity.This paper was carried out to research the impact of four kinds of mould which added during malting of three varieties of barely on malt quality, A negative effect on the solubility of cell wall and intracellular matrix by AlternariaAlte-rnaraKeissler and Neurospore was found, which leaded to the decrease of β-glucanase activity and the increase of β-glucan and turbidity, the turbidity of Gairdner malt effected by Neurospore was the most, increased 220%.Protease activity and kolbach index of three varieties malt added Neurospore all declined, the decrease of the neimonggol barley was the most, reduced 7.2%.