Through analyzing the data of K, Li and B in the mining area of Lake Xitaijinair, the study results revealed the dynamic changes of K, Li and B and their seasons during early mining(from 2003 to 2004).The resultsshow that the changes of contents of K, Li and B in lake brine mainly are controlled by the seasonal changes of surficial runoff. Three elements' contents in underground brine during recovering are higher than those during mining.But their contents in pore brine are higher than those in intercrystalline brine and three elements'spatial differentialion are obviously different. Studies on the phase diagram suggest that the brine during recovering has arrived thestep when the sylvite is precipitating. The brine in mining area is basically in stagnation and there was no signiGcant correlation between water levels and three elements'contents in underground brine. The changes of K, Li andB in underground brine probably are due to the physical and chemical changes of brine itself. And in short time,mining action and surficial runoff' can not evidently influence the elements'changes in hydrochemistry.