The SEFT-H series electro-hydraulic servo in-situ fatigue loading system is a fatigue testing machine equipped with a scanning electron microscope. It is a compact test system for dynamic fatigue testing with hydraulic power as the power source. It is used to observe the surface morphology, organizational evolution and crack extension behavior of the sample in real time during the fatigue test, and can record the stress change law during the fatigue test in real time. Under the scanning electron microscope, the damage mechanism such as phase change behavior, orientation change, crack initiation and extension of the material under stress state can be studied under loading force. It is widely used in aerospace, geology, shipbuilding, biomedicine, electronic devices and other fields. Mechanical testing and analysis of concrete, rock, metal, composite materials, ceramics and other products.