In this study, three novel thermoplastic poly(benzoxazinone-imide)s (PBEI-I, II, III) were prepared by the dealcoholization of the poly(amide–imide)s (PAMI-I, II, III) with an ester group as the pendent group, which were synthesized by a two-step method via the corresponding polyamic acids (PAA-I, II, III) obtained through the reaction of 4,4′-diamino-6-ethoxycarbonyl benzanilide with 2,3,3′,4′-biphenyltetracarboxylic dianhydride, 2,3,3′,4′-diphenyl ether tetracarboxylic dianhydride and 3,3′,4,4′-benzophenonetetra-carboxylic dianhydride, respectively. The imidization kinetics of the PAAs was investigated by differential scanning calorimetry (DSC) followed by simulation with two different kinetic models, Kissinger and Ozawa. For the three PAAs, the activation energy values determined by the models were in the range of 117.56–141.64 kJ mol −1 , the frequency factors were different, and the reaction orders were all approximately one. The value of the activation energy ( E a ) of PAA-I was lower than those of PAA-II and PAA-III, suggesting that the imidization process of PAA-I occurred more easily than those of PAA-II and PAA-III. This is probably due to the fact of the distorted structures in the α-BPDA as the dianhydride made the molecular packing looser and the energy barrier of the collision reaction among the active groups lower, while the presence of biphenyl linkage has a rigid effect. The thermal performances of the thermoplastic polyimides were then investigated by DSC, infrared spectroscopy and thermogravimetry (TG). The results of the DSC and TG indicated that the thermoplastic polyimides including PAMI-I, II, III and PBEI-I, II, III had good thermal properties. The results of the wide-angle X-ray diffraction showed that all the PAMI-I, II, III poly(amide–imide)s were amorphous.