Abstract: Mid-infrared photonic integrated circuits have been attracting a lot of interest for applications in environmental monitoring, medical diagnosis and national defense. However, the integration of laser sources with low-loss mid-infrared waveguide circuits is challenging. Quantum cascade lasers (QCLs) are important semiconductor laser sources operating in the mid-infrared spectral range. In this review paper, the research progress of the photonics integration of mid-infrared QCLs in recent years was introduced. Several different approaches were reviewed, including monolithic integration on InP, monolithic integration on silicon, heterogeneous integration on silicon and III-V/Germanium hybrid external cavity laser.