A novel method for preparing thermosetting modified Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was developed by introducing allyl groups into PPE. It was successfully prepared from the reaction between brominated PPE and a Grignand reagent. The effects of substitution of bromine on methyl group and dosage of allylated Grignard reagent on the substitution value of allyl group were studied. The structure of the resulting allylated PPE (A-PPE) was characterized by H-1-NMR and FT-IR spectroscopy. The curing reaction process was researched by differential scanning calorimetry (DSC), and the properties of the cured A-PPE were also investigated. The curing reaction of the A-PPE was first order reaction. The curing reaction activation energy obtained by Kissinger equation was 121.7 kJ/mol. The cured A-PPE resin is excellent not only in solvent resistance and dielectric properties, but also in thermal properties, moisture absorption and adhesion with glass fiber. The dielectric constant (epsilon) and dissipation factor (tan delta) of A-PPE composites reinforced with E-glass cloth at 1 MHz were measured as 2.84 and 2.65x10(-3), respectively. In addition, A-PPE was very easy to form into films.