This paper describes characteristics of groundwater geochemical anomalies in dry season and rainy season of an arid and desert area in Inner Mongolia. The regional ground water geochemical sampling conducted respectively during the dry season and the rainy season in1981 suggests that the contents of ma jor indicator elements show obvious seasonal changes. Compared with things in the dry season. the peak value of hydrogeochemical anomalies in the rainy season moves toward the lower position, the hydrogcochemieal anomalies al most completely disappear over or near the known ore belts.and the concentra tion centers of the anomalies move to some place far away from the ore belt. Adetailed discussion has been given concerning the influence of evaporation-concentration on the formation and migration of hydrogeochemical anomalies in this area.