Plasmonic nanostructures have great potential for improving the radiation properties of emitters. Here, the plasmonic Au nanorods-PVA nanocomposite films are used to uniformly improve the photoluminescence of Tb/Eu co-doped PMMA film within the local micro-region. Under the excitation of 292?nm, the maximum enhancement factor is 37.2-fold for emission at 612?nm and 21.6-fold for emission at 545?nm. Moreover, the finite different time domain simulations are developed to further explain the experimental results. It is indicated that the modulation of luminescence can be attributed to the increase of the local density of optical states through the Purcell effect and the improvement of the energy transfer efficiency between Tb and Eu. Under the excitation of 360?nm, the maximum enhancement factor is about 71.5-fold. In this case, the Au nanorods are mainly used for modulating the emission process at 612?nm, which deduced a greater enhancement factor at 612?nm. This study provides a deep understanding of the interactions between rare earth ions co-doped materials and plasmonic nanostructures, building a bridge to fabricate a useful platform for several applications, such as thin film-based detectors and sensors.