The article reviews the application of GIS technology to urban planning and the research progress on construction suitability evaluation. It points out that the present evaluation method invisibly weakens high eco-sensitivity areas and unsafe areas, and therefore the evaluation process can not objectively reflect the different angles of urban land use and its contradiction and unity. Thus, the article suggests strengthening the idea of giving priority to ecology and city safety through analyzing key sensitive factors and perfecting multi-factor superposition method. It explores a new idea for land suitability evaluation from three angles, that is, eco-sensitivity evaluation, construction suitability evaluation and city safety. An empirical study is conducted on the master planning of Hongya County Town.