This paper examines the chemical characteristics of spring water and surface sediments in the Mengyejing potash deposit and its surrounding areas, and discusses the genesis of the surface potassium anomaly in the study area. The Mengyejing potash deposit is located in the south of the Lanping- Simao basin in the Yunnan Province, southwestern China. It is until now the only solid potash deposit with industrial mining value in China. Spring water and sediment samples, as well as gas samples from the springs were collected from the study area for chemical and isotopic analysis. Since the salt- bearing strata are widely distributed in the study area, anomaly information can be effectively captured by means of careful surface sample collection, an important factor in the study of the mechanism of potash deposit formation and potassium prospecting. Combined with previous hydrochemical studies, it is proved that the salt spring water in the Mengyejing deposit shows grade I anomaly. The peak and valley values of potassium and concerned components in soil samples from the two profiles perpendicular to the fracture direction show certain regularity. It is inferred that the surface anomalies are somehow related to the recharge of deep fluid (water and gas) along the faults. Noble gas isotopic compositions reveal that the major faults in the study areas may cut deep into the crust and some even into the upper asthenosphere. Hydrogen, oxygen and strontium isotopic compositions of spring water show that the spring water in the study area has deep recharge and water- rock reactions. Additionally, hydrogen and oxygen isotopic composition and mineralogical evidence indicate that deep fluid may play an important role in the formation of the Mengyejing potash deposit. It is inferred that the deep recharge may be an important source for the surface potassium anomaly in the potash deposit, with the volcanic rocks as one of the important material sources, and the fault belts as the controlling factor.