This work was aimed to study the effect of liquid-crystalline epoxy resin content on the curability and mechanical properties of the E-51 resin system. The effect of liquid crystalline epoxy resin on the curing reaction was studied using the method of dynamic DSC. The effects of liquid crystalline epoxy resin on the mechanical properties of cured resin and its toughening mechanism were studied by the method of tensile test and scanning electron microscopy. The higher the content of liquid crystalline epoxy resin, the faster the curing reaction. The impact strength, bending strength and tensile strength were improved by the addition of liquid crystalline epoxy resin. The bending strength and impact strength were the highest when the content of liquid crystalline epoxy resin was 7%. The tensile strength was the highest when the content of liquid crystalline epoxy resin was 10%.