An effective steam-assisted conversion (SAC) seeding method was proposed for the growth of a thin and high-quality SAPO-34 membrane on a low-cost and coarse macroporous alpha-Al2O3 tubular support. This seeding technique was composed of depositing the seeds-containing paste on a support and transforming the paste into continuous and compact seed layer by the SAC process. The paste could serve as the binder to prevent small seeds penetrating into the support. With the aid of the perfect seed layer, a high-quality SAPO-34 membrane with the thickness about 4 mu m was synthesized by secondary growth. The assynthesized membrane exhibited a high H-2 permeance of 6.96 x 10(-6) mol m(-2) s(-1) Pa-1 at room temperature, with H-2/CO2, H-2/N-2, H-2/CH4, H-2/C2H6, H-2/C3H8, H-2/n-C4H10 and H-2/i-C4H10 ideal selectivities of 1.83, 7.58, 14.80, 18.24, 26.51, 40.15 and 53.02, respectively. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.