The isothermal cure behavior of diglycidyl ether of bisphenol A(DGEBA)/4,4'-methylene dianiline(MDA) system with various contents of neopentyl glycol(NPG) was analyzed by differential scanning calorimetry(DSC). To increase the cure rate of DGEBA/MDA system, NPG was used as a accelerator. Regardless of the NPG content, the shape of the conversion curves showed sigmoid, and this meant that DGEBA/MDA/NPG system followed autocatalytic cure reaction. The cure reaction of DGEBA/MDA system increased with the increment of NPG content. This is due to the catalytic role of two hydroxyl groups in NPG and the generated hydroxyl groups of DGEBA/MDA system.