Since Geographic Information Systems (GISs) have been frequently employed in many realms in these years, studies on GIS-based spatial planning and decision has become more and more important nowadays. In Section 1, a short review is given to the applications of GIS in urban and regional planning. In Section 2, a participatory spatial planning based on GIS is introduced. Section 3 is a case study of Yibin City, Sichuan Province, which is the pilot study of National Development and Reform Commission (NDRC). The section is composed of the following five aspects: (a) Introduction of the study area, (b) The formal process of spatial decision, (c) The selection of evaluation criteria, (d) The construction of decision models, (e) The realization of public participation. Section 4 is the last section, the conclusion is put forward and a deep discussion on some existing problems during the research is proposed.