An image projection method for a virtual tour system is disclosed. The virtual tour system receives a panorama image derived from a panorama camera and comprises a local device. The local device comprises a display unit. The method comprises steps of: obtaining a distance factor according to coordinates of the panorama camera and a viewer in real world space; obtaining mapping coordinates of a viewpoint related to the viewer in unit sphere space according to the distance factor and the coordinates of the viewer in real world space; and, forming a view image to be displayed by the display unit according to the mapping coordinates of the viewpoint.