Sandwich structures composed of an ultra-thin gold film, a light-emitting layer and a three-dimensional (3D) photonic crystal (PC) are fabricated by the vertical deposition method and spin-coating method. Attenuated total reflection measurements show that the 3D PC plays a crucial role in the formation of significant optical properties. For the sandwich structure with a high-quality 3D PC, two reflection troughs are clearly observed at the incidence angles of 48° and 63°, while the reflection troughs disappear in the attenuated total reflection curves of the sandwich structures for those with a low-quality 3D PC. Compared with the two-layer structures of ultra-thin gold film and light-emitting layer, pronounced changes are found in the curves of the fluorescence properties of the sandwiches, the single emitting peak at 600 nm of quantum dots (QDs) is split into two peaks, and the intensity of peak positioned at 600 nm is weaker than that positioned at 620 nm by 30%.