In this paper, the trapped field properties of GdBaCuO disk bulk superconductors of various diameters during pulsed-field magnetization (PFM) using an identical split coil at 65 K have been investigated both experimentally and numerically. The maximum trapped field, BTmax, of the Φ43 mm bulk was larger than that of the Φ30 mm bulk. However, BTmax of the Φ65 mm bulk was smaller than that of the Φ43 mm bulk and the trapped field profile exhibited a distorted “C-shaped” profile. Using the numerical simulation, these results for the Φ65 mm bulk can be explained by an inhomogeneous temperature profile and the larger generated heat, Q, due to the lower cooling power of the refrigerator compared to the generated heat. The important issues to achieve higher and homogeneous trapped fields are discussed when using split-coil PFM for larger bulks.