The effect of nanoparticles on the dielectric and spatial charge properties of epoxy resin was studied. The epoxy resin nanodielectrics with different contents of nano-silicon dioxide（SiO

2

） from 0%～5% were prepared by using epoxy resin as a base material and SiO

2

as a filler. The dielectric permittivity and dissipation factor depending on frequency in the range from 0.01 Hz to 1 MHz were studied. The space charge behaviors of samples were also observed under dc electric field of 33 kV/mm. When the SiO

2

concentrations are 0.5% and 1%

ER/SiO

2

nanodielectrics have lower relative permittivity and dissipation factor compared to neat

ER

in the meantime

the accumulation and injection of homocharge were effectively suppressed at the electrode interface. When the SiO

2

concentrations are 2.5% and 5%

ER/SiO

2

nanodielectrics have higher relative permittivity and dissipation factor compared to neat ER in the low frequency region

but the change is not obvious in the high-frequency region. At the same time

the space charge accumulation and the injection at the electrode interface increase significantly. The results indicate that the presence of nanoparticles strongly enhances the dielectric and space charge properties of the epoxy resin

which is influenced by the interfacial region between epoxy and nanoparticles. The interfacial region is the key factor in affecting the electrical performances of ER/SiO

2

nanodielectrics.