Abstract: It is a main direction in the research of underground water to use systermatic analysis method.In the systematic research, of underground water. It is necessary to comprehensively consider various relative falters, such as the relationship anong, hdro 1nanins hdochemistry and thermodynamics system, so that relatively reliable results can be obtained.#br#The theory and practice of the sestematic analysis and research of underground water reveal that many kinds of ions in ground water have mutli-relationship between ++,+-,-+ or between their combination ratios.In this paper, based on the systemetfc study of ratiO relations of ions and their separate-different dynamic change, the variation characteristics and precursor information types of D function of underground water are obtained.#br#It is pointd out that this method is an effective and practical one for extracting and dist-inguishing seismic precusor information from underground water.