The invention relates to a method for controlling growthform of filamentous fungi during a fermentation process and belongs to the field of biological engineering. Detoxification treatment is performed on hydrolysate obtained by performing hydrolysis on lignocellulose, then the hydrolysate subjected to detoxification treatment is added into a fermentation culture medium of the filamentous fungi for performing liquid fermentation culture, and a spherical filamentous fungal group with biological catalytic activity is obtained. By adopting the method, the defects of harsh control conditions for pelletizing of the filamentous fungi, poor repeatability of the control conditions, unstable diameter distribution of fungus balls and the like in the prior art can be solved. The technical means has the advantages that the range of operation conditions is wide, the operation is simple and feasible, and the requirements on equipment can be effectively reduced, so that the technical means has stronger industrial competitiveness than other technical means.