ABSTRACT: Approximately 10 different systems of classification of natural water types were developed. Stuyfzand Classification System combines some features of existing classifications with new, strongly diagnostic criteria for subdivision. And this classification plays very important role for determination of hydrogeochemical evolution of groundwater plain. In this study hydrochemical evolution of Gümüşhacıköy Plain was determined using Stuyfzand Classification System and totally 79 well water, 37 well water analyze results between 1951 and 1972, and 49 well water analyze results between 2003 and 2004, were compared with each other considering this classification system. According to this classification system, the sequence concludes that freshening is going on from NaHCO + to MgHCO +. The south and southwest of the plain is formed CaHCO water type according to the first analyses results but CaHCO + water type dominates theconsequence of freshening to the second analyses results. Typical freshening is going on fromwest to east in time and the composition of the groundwater is turned in to CaHCO +water type.