The siliver clusters films of different coverage rates are generated with a magnetron plasma gas aggregation clusters source, the assembling of films and the space with RH6G molecules can be tuned. The effect of surface plasmon polaritions in the films for use as fluorescence enhancement of molecules is investigated. It shows that fluorescence quenching appears when the films contact closely to the molecules, the silicon nitride spacer is thick enough to avoid fluorescence quenching. When silicon nitride thickness is 15 nm, the fluorescence intensity of molecules is enhanced by 450%. Fluorescence intensity decreases exponentially when the thickness of the silicon nitride spacer increases further.