Different density nitrogen vacancy modified g-C3N4 photocatalysts were successfully prepared, and investigated their photocatalytic performance for H-2 evolution and pollutant degradation. In this system, the increase of nitrogen vacancy density could enable the conduction band position of resultant g-C3N4 to negative shift compared to previous g-C3N4. Meanwhile, various positive factors were also introduced in this system, such as larger surface areas, the improvement of light response capacity, effective separation of photogenerated charge, resulting in resultant g-C3N4 photocatalysts exhibiting evident improvement of photocatalytic performance for H-2 evolution and pollutant degradation. Obviously, this work provides physico-chemical insights for the nature of the promotion effect of nitrogen vacancies. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.