【Objective】The application of straw and biochar is one of the most important measures to improve soil fertility, but whether the abundance of Fusarium graminearum (Fg) concurrently changes during the decomposition process remains unclear. This study aimed to investigate the Fg abundance dynamics with the decomposition process of straw and its derived biochar, and the potential association of it with the variations in properties of organic materials and compositions of fungal communities. 【Methods】An indoor cultivation experiment was conducted by simulating adequate field conditions for Fg inoculum. Four treatments were designed: (1) maize straw (S), (2) biochar plus Fg (BF), (3) maize straw plus Fg (SF), and (4) biochar plus maize straw plus Fg (BSF), among which the maize straw and biochar were added with the equivalent carbon mass. 【Result】Our results showed that the Fg abundance at 7, 21, 42, and 70 days was on average in the order of BF>SF>BSF, and the Fg abundance from the BSF treatment was 84.07% and 69.11% lower than that from the BF and SF treatments, respectively. Correlation analysis showed that the Fg abundance was significantly positively related to total carbon (TC), total nitrogen (TN), total phosphorus (TP), and total potassium (TK) of residual organic materials at 7 and 70 days, and these nutrients were all highest in BF treatment. Besides, the fungal community compositions of organic materials significantly differed between treatments, which were driven by both the Fg abundance and the properties of residual organic materials. We further discovered that the significant enrichment of BF treatment by Dirkmeia and Exophiala may be associated with the occurrence of some plant diseases, while the BSF treatment was remarkably enriched with Sarocladium and has biocontrol potential. 【Conclusion】The above results indicate that the dynamic change of the Fg abundance during the decomposition of organic materials may be mediated by the conjunct effect of the variations in the nutrients content of residual organic materials and it-induced transformation on fungal community composition. Our study provided a novel directive for selecting suitable organic materials to improve soil fertility in terms of the perspective of preventing and controlling Fusarium head blight