We report the reversible conductivity and morphology modulation of PEDOT:PSS composites based on pH. Through studying effects of pH on the morphology and conductivity of PEDOT:PSS composites, it was found that different pH of PEDOT:PSS composites solution will result in different morphology of PEDOT:PSS composites film. At the same time, conductivity of the film also changed accordingly. With the increase of pH from 3 to 11, the microstructure of PEDOT:PSS film reversibly changed from a continuous network to non-continuous clusters, and the corresponding conductivity decreased from 0.62 S/cm to 0.42 S/cm. Furthermore, the mechanism was innovatively investigated by Raman spectra, along with UV Vis spectra and SEM. (C) 2016 Elsevier B.V. All rights reserved.