Carbon layer coated black TiO2-x/g-C3N4 nanosheets (C@TiO2-x/CNNS) heterojunction photocatalysts were successfully prepared via a polydopamine dopamine carbonization route for the first time. It was found that the hydrogen evolution rate of C@TiO2-x/CNNS was 417.2 mu mol h(-1) g(-1) under visible light irradiation, which was much higher than that of other prepared photocatalysts in solar water splitting process at the same conditions, and obvious decrease in catalytic activity can be observed after three recycles. The formation of carbon layer on the surface of TiO2-x can effectively protect Ti3+ and oxygen vacancies (O-vs) from oxidation by air and dissolved O-2, afterwards much more Ti3+/O-vs are exsited, which can serve as charge carrier traps to inhibit the recombination of light-excited electrons-holes. Therefore, C@TiO2-x/CNNS showed a highly conductivity, rapidly effective electron-hole separation and lower transmission resistance comprehensive consideration of the advantages of carbon layer and hetero-junction, which are of great benefit to the improvement of photocatalytic performance. Hence, a new catalytic tactic namely layer-protection effect was founded and this strategy for boosting hydrogen evolution and protection Ti3+/O-vs may give us some hints on the design of photocatalytic systems.