Abstract: The normal and anomalous dynamic changes of radon in Dingxiang spring are systematically analyzed. The radon in Dingxiang Spring shows annually positive bow-shaped change. According to the main influence factors, a hydrological year could be divided into a temperature influence period and a precipitation-pathway stream influence period. The water radon changes seasonally in the short-term and periodically in many years. By using the method of improved hypotaxis function relation, the anomaly of radon in Dingxiang spring is evidently correlated to several strong earthquakes in North China. The change of precursory anomaly was of characteristics of broken-annual change, the correlation change, as well as periodical change in many years and so on, which could act as dynamic judgment symbol of the nature of earthquake precursors. There are similarities and differences between the normal and the anomalous dynamics, indicating that there might be a certain causative relation between them.

Key words: Radon in Dingxiang spring, Normal dynamics, Anomalous dynamics, Nature of earthquake precursor