This paper presents a facile method to fabricate CuS porous microspheres, which were formed by the intergrowth of CuS polycrystalline nanoslices. The obtained sample has been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electronic diffraction (SAED), X-ray diffraction (XRD), UV-vis diffusion reflection and Laser Raman. On the basis of the experimental results, we proposed a self-assemble mechanism to elucidate the formation of CuS nanoslice structure. The current-voltage characteristic under different gas atmospheres shows that the as prepared CuS polycrystalline nanoslices are sensitive to ammonia at ppm level and the electrical conductivity is found to be weaker in ammonia than that in air. (C) 2009 Elsevier B.V. All rights reserved.