Abstarct: Land subsidence caused by the excessive use of groundwater resources has traditionally caused serious and costly damages to the Shahriar plain. Shahriar plain is situated at South and West-South of Tehran plain and is one of the great and important plains of Tehran-Karaj plain. The arrival of surface water is so little and withdrawal of groundwater is so great. In this research a mathematical groundwater model was used to simulate land subsidence caused by the excessive withdrawal of groundwater. In order to optimize the hydraulic parameters, the aquifer was simulated by PMWIN model. The model was run for October 2003 (steady state) and hydraulic conductivity and the transmissivity of the boundaries calibrated. The model was then executed under transient state and the hydraulic parameters such as specific yield were determined when necessary calibrations were done for the model under steady state condition. In the verification stage using observed data for one water year (i.e. 2005-2006); the developed model was run and the results obtained from the model compared with the observed data. Using the model for the maintained one water year showed that it can well predict the land subsidence. The model then predicted land subsidence for six water years (i.e. 2010-2011). According to the obtained results, land subsidence for future years will increase if the atmospheric conditions and withdrawal from water supply wells be constant.