In this study, the groundwater quality of the Meshgin Plain was investigated based on the WQI index and using geostatistical methods. As the results and evaluation statistics of the cokriging method showed, the variogram of the random variable WQI index from the exponential model had a nugget effect (0.02) for the WQI index and (0.05) for the auxiliary variable electrical conductivity. the sill of the variogram for the WQI variable was (0.7) and for the auxiliary variable electrical conductivity was (0.77), which indicates that the role of the structured component of the variogram is greater than the role of its unstructured component, and this indicates the strength of the spatial structure of the region for both the random variables WQI index and electrical conductivity at the regional level. The results showed that geostatistical methods and simple cokriging model, with a coefficient of determination of 0.85 and a root mean square error of 3.27, has an accurate estimate of the WQI random variable. In general, it can be said that the evaluation using the kriging method shows that the WQI index at the regional level is generally at the level of 0-100 and is in the "Excelent" and "Good" quality range, and more than 96 percent of the studied area has good quality for drinking purposes. The results of this study showed that geostatistical estimates are of great importance in determining the WQI index at the regional level,