Abstract: In this paper, the problems about the conditions of the seismic hydrogeochemical, the mainly interference factors, yearly dynamic characteristics, and the relation between the judgement of trend abnormatity and the seismic activity in North China region are Systematicaly analyzed. The study results show that one of the mainly interference factors of water radon observation is the desalination of rain, and that the yearly dynamic rule of water radon is the spring-low and Autumn-high kind. Since the spring water have been abserved in 1979, there are altogether three times of trend high value variation and every variation there correspond the increasing process of the moderate strong seismic activity in Shanxi seismic zone and Huabei region. This indicated that the water radon abnormal variation is related to the increase of the stress field in Huabei region and its regulation process.