A method for manufacturing a hydrodynamic bearing with hydrodynamic pressure generating grooves comprises steps of: step 201: providing a substrate with a first annular protrusion and a plurality of projections formed on a periphery thereof, the projections being in a side of the first annular protrusion; step 202: placing the substrate in a middle of a hollow mold, then injecting a feedstock of powder and molten binder under pressure into the mold to surround the substrate, thus forming a desired bearing preform; step 203: separating the substrate from the bearing preform by means of catalytic debinding; step 204: separating the molten binder from the bearing preform; step 205: sintering the bearing preform to thereby form the hydrodynamic bearing.