Single rare earth doped NaYF4 nanoplate with different size of Ag nanoparticles is designed for the investigation of metal enhanced upconversion luminescence effect. Up to twice enhancement is obtained with big Ag nanoparticles. Luminescence quenching effect is also observed with small Ag nanoparticles. Exploration on the enhancement factors are carried out systematically based on the effect of local field enhancement, the coupling of LSPR with emission band, and even the enhanced far field distribution. It is suggested that the excitation enhancement is the reason for the enhancement at both wavelength. Emission enhancement also took a significant part in the result which is that in the system, the enhancement effect at 540 nm is greater than that at 650 nm. (C) 2016 Elsevier Ltd. All rights reserved.