A high temperature hydrocarbon-degrading strain, Bacillus sp. A1, was isolated from oil-water samples of ShengLi oil field in Shandong Province. The cell-surface hydrophobicity of A1, emulsification to hydrocarbons and change of the wetting property of rocks treated by A1 were investigated in this paper. Three methods were used to determine the cell-surface hydrophobicity, CAM (Contact Angle Measurement), SAT (Salt Aggregation Test) and BATH (Bacterial adherence to hydrocarbon). The results showed that the cell-Surface of A1 was strongly hydrophobic. The diesel oil can be well emulsified by A1, and the emulsion showed good tolerance to salinity, pH and temperature. The hydrophobicity of rocks surface decreased dramatically treated by A1 and the contact angles of quartz, limestone and glass fell more than 60%. If the hydrophilicity of the rocks is higher, the oil in the rocks could be recovered more easily.