Based on the first-principles calculations, the influence of different geometry models on the theoretical results about the electronic properties of LaAlO3/SrTiO3 perovskite heterostructures has been studied. The results show that the superlattice model can indicate n-type conductivity of interfaces, but it is limited to describe the insulator-metal transition of heterostructures. The sandwich and thin film models with the vacuum layer can take into account the surface termination effect on the electronic properties of the interface. The AlO2 or LaO atomic layer as the outmost surface termination is selected during constructing the model, leading to the distinct electronic properties of the heterostructures. The build-in electric filed appears in the AlO2-terminated structure, whereas it does not exist in LaO-terminated structure. Therefore, the AlO2-terminated structure can give a clear description about the insulator-metal transition of heterostructure and the charge transfer mechanism. The build-in electric filed, the atomic rumpling and surface termination effect of perovskite materials codetermine the conductivity of interfaces. The results would be helpful to construct theoretical model and understand the novel electronic properties during investigating other perovskite heterostructures.