In this article, a new catalyst carrier kapok-polyacrylonitrile (PAN) composite microtube was fabricated based on the natural kapok fiber. Kapok-PAN core-shell composite microtubes were prepared by a cetyltrimethylammonium bromide (CTAB) assisted self-assembly method. The formation mechanism was proposed and the influence of the concentration of acrylonitrile (AN) monomer and CTAB on the morphology of kapok-PAN was investigated. The hydrophilicity and specific surface area of kapok microtubes were improved because of the outside PAN coating constructed by the PAN nanoparticles aggregation. Gold nanoparticles (Au NPs) were immobilized on the surface of kapok-PAN microtubes via in situ reduction of chloroauric acid (HAuCl4) by sodium borohydride (NaBH4). The obtained Au NPs with mean diameter of 3.1 nm were well dispersed without any aggregation. In addition, kapok-PAN-Au composites exhibited excellent catalytic activity and could be recovered easily without apparent decrease of activity, as demonstrated via the reduction of 4-nitrophenol to 4-aminophenol by NaBH4. The kapok-PAN composite microtubes may be one of the promising supporting materials in developing low-cost, high-efficiency catalyst carriers for metal NPs. (C) 2011 Elsevier B.V. All rights reserved.