Resin composition, and prepreg and printed circuit board made from same

The invention relates to a resin composition which comprises an epoxy resin and a polymer solution used as a hardener. The resin composition is prepared by the following steps: (a) dissolving a nitrogen oxygen heterocyclic compound in a first solvent to form a first reaction solution, wherein the nitrogen oxygen heterocyclic compound is disclosed as Formula I or II, and R1 to R3, W1, W2, m, n, p and q are defined in the specification; (b) heating the first reaction solution to a first temperature to carry out ring-opening polymerization reaction; and (c) cooling the first reaction solution to a second temperature to substantially end the ring-opening polymerization reaction, thereby obtaining the polymer solution, wherein the first solvent does not react with the nitrogen oxygen heterocyclic compound, the first temperature is higher than the softening temperature of the nitrogen oxygen heterocyclic compound and lower than the boiling point of the first solvent, the second temperature is lower than the first temperature, and on solid basis, every 100 parts by weight of epoxy resin requires 20-200 parts by weight of epoxy resin.