The invention discloses a low-viscosity, low-exothermicity, high-strength, high-toughness epoxy resin / curing agent system for liquid infusion molding of a composite material and relates to the technical field of epoxy resin. The epoxy resin / curing agent system comprises the following components in percentages by mass: 39%-65% of an epoxy resin component, 34%-60% of a curing agent component and 0.1%-1.5% of a curing accelerator component, wherein the epoxy resin component is prepared by uniformly mixing amine-modified epoxy resin and an epoxy resin active diluents; the curing agent component is acid anhydride, the curing accelerator component is a curing accelerator and the total mass of the components is 100%. The low-viscosity, low-exothermicity, high-strength, high-toughness epoxy resin / curing agent system for liquid infusion molding of a composite material has low viscosity of 100-500mPa.s at 25 DEG C, low curing exothermic peak temperature of 90-120 DEG C, tensile strength of 80-90MPa, tensile modulus of 3.2-3.4GPa and elongation at break of 4%-5% and can be used in liquid infusion molding of large-size composite material parts.