Underground water provides the most important water source for domestic, agricultural and industrial use. Produced water from these sources must be very pure in terms of health. The soluble material and the elements should also be low. Physical-Chemical properties together with quality of underground water sources were analyzed in this research for irrigation and drinking uses. Water samples were taken in spring and summer 2010, from 46 deep wells distributed across Southern Khorasan Province. Results showed significantly higher levels of some parameters than the national and international standards. Using Piper diagram, the main water type of the area was determined as Na-SO4, NaCl, Na-HCO3 and Mg-HCO3. The Gibbs diagram also showed the underground water in the area is influenced mostly by interaction with lithology. Factor analysis showed that in autumn, the most influencing parameters on water quality are TDS, EC, Cl, SO4, Na and F while in spring the influencing factors on water quality are TDS, EC, Cl, SO4, and Na. Classification of underground water using Wilcox method for irrigation purposes using Wilcox ratio for EC, Na, S.A.R and Mg showed unsuitability of some wells for agriculture while assessment of total dissolved solids and hardness proved water from wells fall in the range of unsuitable to good for drinking purpose