近年来，农村人口向城镇大量流动加之城镇人口的自然增长，城镇人口对于城镇用地的需求十分强烈；另外，随着经济的发展，城镇固定资产投资逐年增加，致使城镇各业用地需求旺盛。因此城镇的扩张与人口向城镇的流动和政府对城镇的投资是密不可分的。本文试图通过引用系统工程理念中的压力—状态—响应（P-S-R）模型，分析导致城镇建设用地扩张的人口和固定资产投资的压力机制，并构建了测算建设用地需求模型。基于黔江区2004—2008年的数据，测得黔江区合理的城镇扩张规模，避免城镇粗放型的扩张。测得黔江区建设用地增量380.92 hm2。

In recent years, large migration from rural to urban areas coupled with the natural growth of urban population, the demand for urban land is very strong; In addition, with the economic development, urban fixed asset investment increased year by year, resulting in strong demand for urban land use in various sectors of society. The migration of population and government investment play an important role in urban sprawl. To prevent the extensive urban sprawl, this study analyzed the pressure mechanism of the population and fixed asset investment that led to the urban expansion, and built a demand model that could estimate construction land. Based on the data of 2004-2008, the reasonable scale of Qianjiang town was obtained by using P-S-R model, and the extensive expansion of the town was prevented. The increments of Qianjiang construction land was 380.92 hm2.