Dielectric properties (dielectric constant and loss factor) of Australia lignite were determined using an impedance analyzer and other instruments over the moisture contents of 8-48%, temperature of 25-100 degrees C, and frequency of 1-50 MHz. Both dielectric constant and loss factor of lignite samples increased monotonically with the increase of moisture content at all temperatures and frequencies. Dielectric constant increased with the increase of frequency, and loss factor changed quadratically: first decreased and then increased. Dielectric constant increased with the increase of temperature at low moisture contents (8-28%), but it decreased at high moisture contents (38-48%), and loss factor increased with the increase of temperature at all moisture contents. The penetration depth of radio frequency energy of Australia lignite was obtained through the equation. It decreased with the increase of moisture content, temperature, and frequency.