Abstract: High-density polyethylene (HDPE) composite films filled with different carbon nanotube (CNT) contents were prepared by melt mixing and molding.The dielectric propereties of the composite films were investigated at different temperatures and frequencies.Results show that the dielectric permittivity and the loss of composite strongly depend upon the filler content,frequency and temperature.The permittivity of pure HDPE is slightly dependent on frequency and temperature in a frequency range of 10³~10⁶ Hz and temperature range of 40~130℃,but the permittivity of composites decreases with the increasing of frequency and temperature.The alternating current (AC) resistivity of composites shows a strong dependence on frequency when the filler mass fraction is under 0.5%.While the filler mass fraction is more than 0.5%,the resistance varies with frequency changes,exhibiting direct current (DC) characteristics in the low frequency region,and AC resistivity decreases at high frequency.