Using high temperature-optical microscopy, in situ investigations were conducted on melting and superheating behaviors of REBa2Cu3O7- (RE123, RE = Nd, Gd) films, which were grown on nano-layer buffered substrates. The results demonstrate that all buffered RE123 films have improved crystallinity and in-plane alignments, leading to the higher superheating capability. In the first case, due to its good lattice match with the buffer material of Y123, the Nd123 film with the minimal extrinsic property grew from the superior interface. In the second circumstance, because of its stronger chemical bonding with the buffer layer of Gd2O3, the pure c-axis oriented Gd123 film was fabricated. Moreover, the optimized thickness of buffer layer plays an important role in reducing interface energy of RE123 films and enhancing its superheating capacity.