The structural aerogeochemistry process along the earthquake-generating fault of the Haiyuan (M_S8.5 earthquake) in 1920 is discussed based on the exprimental result.The degassing on the Haiyuan active fault is mainly crust degasification,in which the contents are mainly from middle-upper crust.The degassing intensity is closely correlated to the fault stress state as well movement characteristics.The different degassed elements reflect different depth and characteristics.Radon reflects shallow depth and tension,mercury and Helium reflect relative deep depth,and hydrogen reflects obduction or nappe or rock-water reaction on the fault surface.