Abstract: In recent years,because of rapid social economic development and increasing  demand for construction land in Xiangxi Autonomous Prefecture,imbalance between the  supply of and demand for construction land has become increasingly acute.Determining a reasonable construction land scale is significant for  sustainable development of the local economy.This article analyzes the cause of expanded demand for construction land in Xiangxizhou and the mechanism of investment pressure on fixed assets using PSR model in system engineering.A PSR model for demand for construction land is established.Based on the data from 2000 to 2008,this article concludes that demand for construction land will be 3 233 hm2 in Xiangxizhou from 2008 to 2020.

Key words: PSR model, construction land, demand, control, Xiangxi Autonomous Prefecture