The invention relates to an epoxy resin composition as well as a prepreg and a laminated board made of the same. The epoxy resin composition comprises the following components in parts by weight: 1-50 parts of modified polyphenylene oxide resin, 30-80 parts of epoxy resin, 20-60 parts of active ester curing agent, 0-50 parts of filler and 1-20 parts of assistant. The prepreg made of the epoxy resin composition comprises a base material and the epoxy resin composition which is attached to the base material through soaking and drying. The laminated board made of the epoxy resin composition comprises a plurality of laminated prepregs, wherein each prepreg comprises a base material and the epoxy resin composition which is attached to the base material through soaking and drying. The invention has the advantages of high heat resistance, high fire retardancy, low dielectric constant, low dielectric loss, excellent high-frequency dielectric properties and the like, and is suitable to be used as a high frequency circuit substrate material.