Considering that the subsurface drip irrigation system is developing in the orchards, it is necessary to investigate the salinity changes in the root-zone development area. Three pistachio orchards with subsurface drip irrigation systems were selected. Using the Hydrus 2D model, soil salinity changes were simulated and compared with the measured values. Soil salinity in near zoon of lateral is minimum and soil salinity wheat increasing distance of drippers has been increased. In the high salinity of irrigation water (8.5 dS/m) the pattern of soil salinity in surface layer increase and this increment is higher than salinity threshold value of pistachio trees. In low irrigation water salinities (2.5 and 3.5 dS/m), the salinity variations in the surface layer of the soil are not so great that causes salt accumulation. The cumulative results of the normalized root mean square error index of soil salinity changes(compared between measured and simulated values) by the model are 17% and indicate the efficiency and accuracy of the model in simulating soil salinity in subsurface drip irrigation. in order to determine the pipe installation depth and drippers in subsurface drip irrigation system, it is necessary to identify the soil salinity variations at the surface and depth, as well as the depth of root development, and it can produce the effectiveness of this system on irrigation efficiency, yield and finally, increase agricultural water productivity.