The mid-infrared (MIR) quantum cascade lasers (QCLs) have been widely applied in the fields such as directional infrared countermeasure, free-space optical communication, trace gas sensing, and other important fields. We further improve the theoretical approach for self-consistent solution of the Schrdinger equation and the Poisson equation based on the MIR QCL device using the Nextnano++ software. We calculate the electronic subband structure in the active region of the four-level and double-phonon resonant QCL structure for GaInAs/AlInAs multi-quantum well-based MIR QCL devices grown on InP substrate. The dependence of these subband energies upon device operating temperature, driving electric field, and doping concentration in the injection region are studied. Theoretical findings are in line with the experimental results. This work provides theoretical design and research methods for the growth and preparation of MIR QCL devices, provides theoretical expectations for understanding the working conditions of devices, and provides theoretical research support for further improving the luminescence power and efficiency of MIR QCL.