g-C 3 N 4 /Ag-ZnO (CAZ) composite photocatalysts were synthesized successfully by the hydrothermal method. The photocatalytic performance of photocatalysts was assessed through experiments measuring both hydrogen (H 2 ) production and the degradation of methylene blue (MB). The H 2 production rate of 60% CAZ reached 2.450 mmol•g −1 •h −1 , which was 8.5 times that of g-C 3 N 4 . 25% CAZ degraded 99.14% of MB dye within 40 min, and its degradation rate constant was 12.4 times that of g-C 3 N 4 . CAZ composite photocatalysts have good synergistic properties in degradation and hydrogen production and exhibit better photocatalytic performance. A Z-scheme photocatalytic system mechanism of CAZ has been proposed for the enhanced H 2 production and photocatalytic degradation rate.