Influence of defect on photocatalyst is in extensive concern. In the present contribution, by cold plasma treatment (CPT) technique and dip-coating method, we successfully prepared ZnO bilayer films with oxygen vacancies and interstitial zinc atoms. The defective films showed promoted photocatalytic activity, with enhanced transportation and good separation of photogenerated charge carriers being the main reasons. More importantly, combination of CPT and dip coating method allowed us to investigate the dominance of defect and its stability. Our work may not only provide helpful information for better understanding of relationship between defect and photocatalysis, but also offer a new strategy for designing stabilized defect-modulated photocatalyst. (c) 2013 Elsevier B.V. All rights reserved.