The scattering rates of carriers in ac tive region of the Terahertz quantum cascade lasers (THz QCLs) are crucial param e ters for studying the carriers′ transport machanisms and for device simulation and optimization design.In this paper,a self-consistent solution with Fermi′s g olden rule is presented to calculate the scattering rates in active region of TH z QCLs.Electron-LO-phonon scattering,electron-electron scattering and electro n-photon scattering are all taken into account in calculation process.This appr o ach is extremely useful when studying the transport mechanisms in the active reg ion of THz QCL by using the rate equation method.By using this approach,the scat teri ng rates are calculated for two THz QCL devices,and the lattice temperature and injector doping impacts on scattering rates are also investigated.The simulation results are in agreement with reported theoretical and experimental data,which proves the practicality and accuracy of the approach.