Solid?state femtosecond lasers are widely favored by the market due to their small size, low cost, long service life, high stability, and relatively mature technology. Repetition frequency is an important parameter of femtosecond lasers. In practical applica?tions, high repetition frequency can bring many important advantages such as high efficiency and high precision. This paper introduces the commonly used mode?locking technologies and development of GHz solid?state femtosecond lasers such as SESAM mode?locking, KLM mode?locking and high?order harmonic mode?locking, and expounds the performance advantages of GHz femtosecond light sources in application scenarios such as laser processing, distance measurement and spectrum measurement. It also predicts the deve?lopment direction of GHz repetition rate solid?state femtosecond laser technology, and provides reference for promoting the improvement of GHz repetition rate solid?state laser technology.