This paper analysis some inadequate places of existing design theories and methods for fatigue cracking of steel bridge deck pavement epoxy asphalt concrete , based on fracture mechanics and energy method principle, proposed impact toughness as epoxy asphalt concrete mix design evaluation index, and verify the feasibility of this indicator by testing; use residual stiffness modulus ration to reflect the epoxy asphalt concrete fatigue performance, establish relationship between impact toughness and residual stiffness modulus ratio. The results show that there is a good linear correlation between impact toughness and fatigue property , it can evaluate the epoxy asphalt concrete mix design and fatigue performance effectively to use impact toughness index . The method is simple, fast, accurate, can provide a new idea for epoxy asphalt concrete design theory and method.