Abstract: The study aims to estimate the role of cell wall degradation enzymes in the pathogenic processes of apple mouldy core caused by Alternaria alternate and Trichothecium roseum. The authors used the‘Starking’ apple as the material. Cell wall degradation enzymes produced by Alternaria alternate and Trichothecium roseum both in vitro and in vivo were studied. The commercial cellulase and glucanase preparation were placed on the‘Starking’apple to observe the disease incidence. The results showed that different levels of enzyme activities were obtained with A. alternate and T. roseum grown on different carbon sources. The induced activity of T. roseum filter paper enzyme was the highest in apple cell walls powder. The induced activity of A. alternate filter paper enzyme was higher in apple cell walls powder and cellulose than that of other treatments (P＜0.05). The induced activity of A. alternate and T. roseum carboxymethyl cellulose both were the highest in apple cell walls powder (P＜0.05). The induced activity of A. alternateβ -glucanase was the highest in apple pulp. And the induced activity of T. roseumβ - glucanase was the highest in apple pulp and cellulose. The commercial cellulase and glucanase preparation placed on pricked fruit led to the formation of symptoms similar to those developing on A. alternate and T. roseum inoculated fruits, and the incidence area were 2.46 and 0.75 cm2 after inoculation 3 d, respectively. These results demonstrated that the cellulase and glucanase played an important role in the pathogenic processes of apple mouldy core caused by Alternaria alternate and Trichothecium roseum, especially the cellulose.