Cuprous oxide (Cu2O) nanoparticles with various particle shapes were synthesized via colloidal chemistry approach. Using ascorbic acid as a reducing agent and polyvinylpyrrolidone (PVP) as a surfactant, cuprous oxide monocrystalline nanoparticles with various sizes have been successfully synthesized by reaction of bivalent copper in aqueous solution. The samples were characterized by XRD, SEM and UVs spectroscopy. The results indicate the shape of as-prepared cuprous oxide nanoparticles has close relationship with thermodynamic conditions, kinetic conditions and stirring rate. Self-assembly mechanism of cubic cuprous oxide monocrystalline nanoparticles has also been investigated. (C) 2012 Elsevier B.V. All rights reserved.