Cure kinetics of epoxy resin E51/MP/methyltetrahydrophthalic anhydride (MeTHPA)/ 2-ethyl-4-methyl-imidazole (2,4-EMI) flame retardant composite were studied using the dynamical tortional vibration method. The influence of MP loadings on the cure behavior has been studied and the kinetic parameters such as apparent activation energy were calculated as well. The results showed that the rate of cure reactions depended distinctly on the cure temperature. At low MP loadings, the gelation time tg for the systems did not change obviously while at higher MP loading (higher than 20 phr) tg had a remarkable increase. Furthermore, the Flory's gelation theory and Avrami equation could be used to describe the cure behavior of epoxy composite system.