By controlling the sintering temperature of Gd211 solid pellet, a series of Gd211 precursors with different microstructures were obtained. On this basis, Single domain GdBCO bulk superconductors have been successfully fabricated by the top-seeding melt infiltration growth process. Through observing the macro morphology and microstructure of the GdBCO bulk and the Gd211 precursors, as well as measuring the magnetic levitation force of GdBCO superconductor, the results show that It was only when the microstructure of the precursors block meet conditions: Gd211 particles are spherical or ellipsoidal and the average size is smaller. The gaps between Gd211 particles are appropriate. The size of Gd211 particles in the single domain GdBCO bulk superconductor is the smallest, The magnetic flux pinning and levitation force of the sample is the largest(The maximum force is 38.7N, The sample diameter is 20mm, The test temperature is 77K, The permanent magnet diameter is 20mm,The surface magnetic field is 0.5T). The results provide scientific basis and ideas to improve the superconducting properties of HTS.