The mid-infrared band has broad applications, such as fundamental science, biomedicine, environmental testing, national defense, security, communications, and entertainment. As the core component of mid-infrared technology, a high-performance mid-infrared coherent radiation source with a wide spectral range, high energy, high conversion efficiency, miniaturization, and room-temperature operation has been a research focus in scientific research and application. There are many types of mid-infrared lasers. According to different generation principles, mid-infrared lasers are mainly divided into chemical lasers, gas lasers, and lasers based on rare earth or transition metal ion doping, quantum cascade semiconductor lasers, and lasers based on nonlinear frequency conversion. This paper focuses on the characteristics and development of these lasers and discusses their research prospects.