Abstarct: Birjand plain The main plain in south Khorasan, encompasses 33% of the population of the prorince. Total area of its basin is 3435 km2 and area of the aquifer is 306 Km2. The average annual rainfall and temperature in Birjand plain are 140 mm and 16.5ºC, respectively and the climate is arid. Drinking water of Birjand city is mainly suplied from groundwater resource. Prilcing wells are located in urban and sub- urban area, as it increases contamination possibility. Regarding this, the aim of the study was to analyze the wellhead protection area (Capture zone) of municipal wells in Birjand aquifer using WhAEM2000. Wellhead protection area of the wells was calculated by Arbitrary Fiexed Raduse (AFR), fiexed radus (CFR), uniform flow and flow boundary method. baxsed on engineering judgment in AFR method a distance of 300 m was selected for drinking wells in Aliabad and Rekat area. In CFR method the average radius of 650 m for Rekat and 750 m for Aliabad were calculated as 20- year capture zone of drinking wells. The minimum and maximum length of 20- year capture zone in flow boundary method was determined as 0.98 and 3.8 km respectively .Flow boundary method, in which calibrated method is used and local hydrogeological conditions are considered as well, has higher accuracy and was selected as the reliable method drinking wells. The capture zone has an elongated shape in this method. baxsed on calculated capture zone wells near industrial estate and in birjand city area, are most exposed to contamination and more attention must be paid to protect them.