A displacement damage detector is designed and its characteristics are tested with 10 MeV proton irradiation. The testing result shows that the detector's readout changes linearly with the fluence of proton beam up to 10(12) proton/cm(2). However, a significant damage enhancement factor has been observed for 1.8 MeV electron irradiation when the classic non-ionizing energy loss (NIEL) is used for calculating equivalent displacement damage. Since the prediction based on classical NIEL model cannot fit low energy incident well, low energy particles induced displacement damage mechanism, defect generation, recombination and effective NIEL modification is discussed by molecular dynamics (MD) model. The effective NIEL is validated by measuring the detector's response under 1.8 MeV electron irradiation. The equivalent displacement damage between different particles is discussed through scaling factor, damage factor, and damage enhancement factor. By this method, the application of degradation function can be expanded to low energy particles by using effective NIEL.