A composition control and formation of InN/WO3 nanocomposite on the as-grown In2O3 by in-situ reactive plasma annealing was investigated. The reactive plasma annealing changes the facets crystalline In2O3 structure to nanograin structure of InN/WO3 nanocomposite with the grain size of 100-200 nm. X-ray photoelectron spectroscopy (XPS) reveals the formation of In2O3, InN and WO3 nanostructures in the nanocomposite. In-situ reactive plasma annealing enhances the removing of In2O3 and facilitates the formation of InN/WO3 nanocomposite. Furthermore, the reduction of oxygen in In2O3 leads to a decreasing in optical energy gap from 2.91 to 2.63 eV. (C) 2016 Elsevier B.V. All rights reserved.