CuS hollow spheres have been synthesized through a facile microemulsion template route at room temperature using copper naphthenate as metal precursor and thioacetamide as the source of S 2− . In our method, the metal precursor and sulfur source dissolved in two different phases; the reaction only occurs at oil/water interface. Thus, hollow spheres can be fabricated more easily. The CuS hollow spheres prepared at room temperature are loose aggregates which are composed of small primary nanoparticles. To form stable hollow spheres it is a key to ensure the growth of nanoparticles at initial stage of reaction by a high interfacial reaction rate. So the reaction conditions that can control interfacial reaction rate are important factors for forming hollow spheres.