The effects of radial temperature gradient on the macrostructure and properties of MTG bulk YBCO superconductor have been investigated. The results indicate that a positive radial temperature gradient is favourable for depressing the nucleation number of YBCO bulk superconductors during the MTG process. Samples fabricated in this way is composed of a few large fan-shaped YBCO Superconducting crystal domains, and its magnetic levitation force is higher. On the contrary, a negative radial temperature gradient is favourable for randomly nucleation, and produces a sample with many small crystal domains randomly oriented. The magnetic levitation force of the sample is lower.