The present invention relates to a method of loading 3-D image data in a navigation system. In the method, whether a vehicle enters an intersection while traveling is determined. A mask array based on a travel path of the vehicle is selected. An object to be displayed at the intersection is selected and a level-of-detail array of the object is selected according to a distance between the vehicle and the object. The level-of-detail array of the object overlaps the mask array. The object is displayed according to a level of detail of the object obtained from the level-of-detail array overlapping the mask array. According to the method, real-time 3-D image data can be loaded in a simple and efficient manner.