Abstract: A tracer diffusion device includes: a first container, for holding a first fluid containing a tracer; a second container, for holding a second fluid; a drilling pipe; wherein, a first end of the drilling pipe is connected to the first container; a second end of the drilling pipe is extended into a borehole; and the second end of the drilling pipe is equipped with a first sealing capsule and a second sealing capsule; a plurality of through holes are arranged on the drilling pipe between the first sealing capsule and the second sealing capsule; a unidirectional driving device, arranged on the drilling pipe, for injecting the first fluid from the first container into the borehole between the first sealing capsule and the second sealing capsule; and a bidirectional driving device, arranged between the second container and the first sealing capsule.