Cornstalks, as a kind of cheap substrates, can effectively reduce the cost of bioflocculant’s synthesis. With 1.7％ of dilute sulphuric acid hydrolyzing cornstalks, the hydrolysate containing pentose-xylose and hexose-glucose can be produced. Pentose is difficult to be metabolized by microorganism; obtaining strains which metabolize pentose and hexose synchronously from cornstalks are the key to converse of bioflocculant. This study, based on cornstalks hydrolysate as substrate in screening flocculation Strain W4, explored its ability of synchronous metabolism pentose and hexose. The results revealed that Strain W4 was identified as Bacills subtilis via 16S rDNA. The metabolic rate of glucose (0.27 g·L-1·h-1) by Bacills subtilis exceeded the rate of metabolism of xylose (0.14 g·L-1·h-1), indicating Strain W4 can produce synchronous metabolism of xylose and glucose. The flocculation rate in synthesizing bioflocculant of Strain W4 from xylose and glucose mediums were 96％ and 97％ respectively. The main components of bioflocculant W4 were polysaccharide and protein through the analysis of FTIR (Fourier transform infrared spectroscopy).