Mesostructural transformation and deformation of vanadate -hexadecyltrimethylammonium composite powders by thermal treatment were investigated. This composite, prepared from vanadate and surfactant solutions, had a lamellae-like structure and displayed mesophase transformations to two-dimensional monoclinic (p2) and hexagonal (p6m) structures during calcination at 160 degreesC. The formation of the p2 mesophase was found for the first time in the self-organization processing system. The origin of the phase transformation was confirmed by thermal analysis to result from removal of the organic component during the heat treatment. It is speculated that those results are due to the strong interaction between the inorganic framework and the organic template.