Abstract: Cellulose is the largest stock of biomass on Earth. It is a research hotspot in the field of biomass to functionalize and develop new applications. A cellulose-based antibacterial hydrogel was prepared and proved to have good inhibition effects on two common plant disease fungi by plate bacteriostatic experiments. Firstly, the optimum oxidation conditions were obtained by oxidizing cellulose with sodium periodate and the oxidation degree was measured. Secondly, the oxidized cellulose was reacted with polyethyleneimine to produce hydrogel, and the hydrogel suspension with a mass fraction of 1.0% was prepared by high speed homogenization. Finally, the bacteriostatic effects of the cellulose-polyethyleneimine hydrogel (PEI/OC-gel) against Pyricularia grisea and Fusarium oxysporum f.spniveum were evaluated. The results show that the PEI/OC-gel could efficiently inhibit the growth of Pyricularia grisea and Fusarium oxysporum f.spniveum when the concentration was over 0.75 mg⋅mL⁻¹. It is expected to be used to control common plant fungal infections such as rice blast and watermelon blight.