All-solid-state single-frequency lasers with long coherent length, narrow line width, high efficiency and long life time have been widely used in scientific, military and industrial fields in recent years. The key techniques to achieve the all-solid-state single-frequency laser output and improve the laser performance are single longitudinal mode selection and power amplification. The domestic and international progress in such lasers and the mainstream technology programs are analyzed and summarized. In addition, the prospect of the all-solid-state single-frequency laser is discussed.