A blend of 2,2′-bis(8-allyl-3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl) propane (Bz-allyl) and N,N′-(2,2,4-trimethylhexane-1,6-diyl) dimaleimide (TBMI) was prepared. The curing mechanism and thermal property of the cured blend were studied with Differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) and Dynamic mechanical analysis (DMA). It was found that in BzT11 the thermal polymerization reaction of TBMI, the reaction of TBMI catalyzed by Bz-allyl, Ene reaction between TBMI and allyl groups occurred at a low temperature (160 °C) simultaneously. About 20% of TBMI was consumed by Ene reaction. Besides, seldom oxzine ring of Bz-allyl polymerized at a low temperature (160 °C) and most oxzine ring of Bz-allyl reacted at a high temperature (over 160 °C). The Tg of cured blends was increased with the increment of the proportion of TBMI in the blends.