Abstract: Pretreatment is the most expensive and critical step of converting biomass into energy, while biological pretreatment has attracted extensive attention for its environmental friendliness and low energy consumption. In order to find a bacteria efficient for use in biological pretreatment, degumming efficiency was chosen as the scale for strain screening. A strain, coded as A₁, was isolated from the environmental media where Eichhornia crassipes grew through enrichment culture and primary screening with the Congo red plate staining method, and tested to be a strain quite efficient in degumming water hyacinth. Under the optimal conditions, Strain A₁ could secrete pectinase, xylanase and cellulase as high as 3 925.00, 8 331.67 and 4 883.62 nmol·s^-1·mL^-1, respectively, in activity. When used in pretreatment, it could reduce the weight of water hyacinth by 33.37% through one round of degumming, and cumulatively by 49.26% after three rounds of degumming. The strain was identified as Bacillus amyloliquefaciens by means of 16S rRNA sequencing and phylogenetic tree analysis.