A method for positioning a portable communication device is provided. First, the signal intensities of a plurality of base stations near the portable communication device receiving radio waves from the base stations are detected, and coordinates of the base stations are found in order to calculate a position coordinate of the portable communication device through the coordinates and the signal intensities of the base stations. Then, the values of a plurality of environmental features between at least one of the base stations and the portable communication device are obtained from a geographic information system (GIS) according to at least one coordinate of the base stations and the position coordinate of the portable communication device. After that, the signal intensities of the base stations are modified by substituting the values of the environmental features into a path loss model. Finally, the position coordinate of the portable communication device is recalculated according to the modified signal intensities of the base stations thereby enhancing the positioning accuracy substantially.