We have systematically investigated the localized surface plasmon resonance (LSPR) of the silver nanoparticles by using electron energy loss spectroscopy (EELS) and optical simulation based on boundary element methods with respect to the diameter and the impact parameter variations. The both peaks of EELS and optical curve were occurred from 3.2 to 3.8 eV. Interestingly, we found two types of plasmon modes. At the impact parameter from 0 to R, the plasmon showed the properties as bulk plasmon, while at the greater value than R it showed the surface plasmon mode. This result showed the EELS simulation was better to observe a high-order of LSPR spectra than optical simulation. High-order was originated from a higher multipolar mode and weak interaction in surface plasmon phenomenon. As shown above, the EELS measurement can detect a high-order mode of LSPR than the optical measurement.