Abstract: the short-term variation characteristic of groundwater dynamics has been studied deeply.The long-term variation characteristic is studied with the monthly mean data of groundwater level variation recorded in the 6 wells in Tangshan region from 1982 to Sep., 2001.The results show that the dynamic variation of groundwater in many years and large space is a smooth random course, with a periodical structure about 10 years.The structure is not relevant closely to geological tectonic environment, hydrogeologic condition, geographical physiognomy, surveying layer, recharge and discharge condition and the distribution of surveying wells.This phenomenon may be relevant to complicated holographic celestial motion, which is a stack of many kinds period, or may be an action of resulting force representing the local stress field.