Nowadays in dry areas such as Iran, groundwater is considered a large supply for drinking and agriculture water and the drought crisis in the recent years makes it more important. The greatest danger that threatens the future exploitation of groundwater resources is contamination by hazardous substances that are released in natural environment due to negligence. Considering that the most important water supply in Buin-Daran plain is groundwater, in the present study the hydrological and hydrogeological status of the plain is examined. For this purpose, Modflow software was used to make the qualitative and quantitative plain aquifer model. Because of the importance of groundwater and natural and unnatural pollution in the use of these resources as sources of drinking water is important, the alarming nitrate factor was considered. Nitrate in the plain groundwater was sampled quarterly in a year from 42 wells with suitable dispersion. The quantitative Modflow model was made under steady and unsteady flow states and was verified foe a two-year period (Farvardin 92 to Esfand 93). The qualitative aquifer model was made and verified for nitrate polluting factor using Modflow software. By comparing the data obtained from quantitative and qualitative models with observed data, the accuracy of the model was evaluated using two parameters (R 2 and RMSE). DRASTIC model was used to study vulnerability of Buin-Daran plain against polluting factors and ArcGIS software was used to process and analyze aquifer quality. In DRASTIC model, inherent and special vulnerability were calculated using effective characteristic in aquifer vulnerability assessment such as water table depth, feeding, aquifer kind, soil type, topography, unsaturated regional ingredients, hydraulic conductivity and land use that were implemented as eight layers in ArcGIS software. After weighting and ranking layers, the final map of zoning the aquifer to pollution, 5 regions were obtained ranging from no risk vulnerability region to very high vulnerability region. Inherent vulnerability index for the entire area was estimated between 69 to 143 that reflects the high inherent vulnerability of the aquifer. Special vulnerability index was calculated in range of 120 to 160 that shows the use of nitrate fertilizers as the main vulnerability factor of the plain. By analyzing sensitivity of effective parameters in vulnerability assessment of the plain, depth and sheer feeding parameters were identified as the most influential parameters. Nitrate ion and the outputs of Modflow model were used for validation of the DRASTIC model outputs and it was found that all points that have a high nitrate content are in the range of high vulnerability that could confirm the accuracy of the model. Keywords: DRASTIC, Modflow, Nitrate, Vulnerability, ArcGIS, Buin-Daran