Plasmonic enhancement by of light-emitting materials by metal nanostructures have attracted wide attentions for decades in variety of fields of science including bio-sensors, imaging applications, photonic circuits, light-emitting devices (LEDs) and so on. In the case of LEDs, which are becoming an alternative general light source with huge potential energy savings, plasmonic enhancement of the active layer in epitaxial LEDs and organic LEDs have been studied extensively over the years. On the other hand, the interaction between metal nanostructures and optical down-conversion form of LEDs such as quantum dot LEDs (QD LEDs) have yet to be studied in detail. Analysis of the mechanisms of excitation enhancement, spontaneous emission enhancement and quantum efficiency enhancement process between QDs and localized surface plasmons (LSPs)is carried out by series of in-depth simulations and calculations to predict how much enhancement factor can be obtained. The predicted values are confirmed by experiment by using a blue LED as the excitation source, green QDs and red QDs coupled with hexagonally arranged array of aluminum nanodisks and silver nanodisks, respectively. Calculations for achievement of white light emission was also carried out. We believe that this research is viable for applications in the efficient color-conversion applications such as QD televisions and micro-displays for virtual and augmented reality applications while reducing the production cost significantly.