Abstract: The application of polymer is limited by its relaxations behaviors. The main research of this paper was focused on the effect which the aluminum trihydroxide (ATH) filler has on α relaxation and β relaxation of epoxy composites. And the broadband dielectric spectroscopy technology was applied to investigate such effect in this paper. In our experiments, the test condition was that the broad frequency of broadband dielectric spectroscopy ranged from 0.1 Hz to 2 MHz and the temperature of the broadband dielectric spectroscopy was from-100℃ to 100℃, also the inorganic filler must be the ATH powder with the particle size of 2 μm. The pure epoxy resin and the epoxy resin to which was added different proportion (0%, 20%, 40%, 60%, 80% and 100%) of the fillers were prepared and the dielectric properties of each of them was measured. The results show that, the quantities of the inorganic fillers have little effects on α relaxation but have an obvious and significant effect on β relaxation. With the quantities of the inorganic fillers increasing, the Vogel temperature decreases at first and then increases. On the contrary, the β relaxation apparent activation energy of ATH/epoxy composite increases at first and then decreases.