The invention discloses a method for predicting plant biomass based on different water flow velocities and belongs to the field of aquatic biological engineering. The method comprises the following steps: (1) cultivating a plurality of to-be-tested plant seeds in regions with the same condition and injecting water into the planting regions; (2) setting propellers in water, and setting multiple groups of different propeller frequencies corresponding to different water flow velocities and a static group in the planting and growth process of the multiple groups; (3) measuring the plant biomass of the corresponding group every several days; (4) drawing a plant biomass and time relation graph; (5) establishing a logistic equation with the water flow velocity; (6) changing the equation into a formula (the formula is as shown in the description), wherein a, b, c and d are model parameters; (7) obtaining the values of regression equation coefficient, namely a, b, c and d, through fitting of actual measured values; (8) obtaining the change result of plant biomass under the influence of the water flow velocity. By the method, the plant biomass at the corresponding the flow velocity can be predicted quickly according to different flow velocities, and the accuracy degree is high.