Pulsed field magnetization (PFM) and field-cooled magnetization (FCM) have been carried out for GdBaCuO disk-shaped bulks fabricated by two-step buffer-assisted (BA)-top seeded infiltration growth (TSIG) technique, and the results are compared with those of bulks fabricated by conventional top seeded melt growth (TSMG) technique. In both PFM and FCM experiments, the two-step BA-TSIG bulks showed higher trapped field properties than the TSMG bulks and, in particular, the maximum trapped field by PFM was over 3.5 T at 40 K using a split-type coil with soft iron yokes. The magnetization efficiency, BTmax/Bapp*, was defined to evaluate the trapped field efficiency quantitatively, where BTmax is the maximum trapped field and Bapp* is the optimum applied field to achieve BTmax at each operating temperature. A high efficiency over 80% was achieved for the two-step BA-TSIG bulks at 40 K, which was nearly 10% higher than that for the TSMG bulks. These results were due to the high critical current density, Jc, and the thinness of the two-step BA-TSIG bulks, readily causing flux jumps to assist in achieving higher trapped fields.