Accurate detection and measurement of magnetic fields, especially extremely weak magnetic fields (below nT level), plays a better auxiliary role in understanding the physical world. With the development of quantum sensing, information, instrumentation and other technologies, atomic magnetic field measurement technology has become the development direction of a new generation of ultra-sensitive magnetic field measurement technology. In this paper, the signal measurement, modulation methods, research progress, design scheme and practical application of atomic magnetometer are summarized. Firstly, the research status of atomic magnetometer at home and abroad in recent years is introduced. Secondly, the basic principle of all-optical atomic magnetometer is discussed. Thirdly, the principle of weak magnetic signal detection is explained in detail and different modulation methods are compared. Finally, the direction of improvement, application fields and challenges of high sensitivity de tection of weak magnetic signal in the future are prospected.