The ZnO QDs/graphene nanocomposites materials enhance formaldehyde sensing properties by 4 times compared to pure graphene at room temperature. The sensing enhancement can be attributed to the synergistic effect between the graphene and the ZnO QDs. The decorated ZnO QDs play a role as catalytically active centers, and the graphene acts as a conducting network and response to the transferred electron for formaldehyde as sensing signals.