The real-time acquiring and processing technology of three- dimension (3D) geosciences information is an important field of modern remote sensing. The Airborne Scanning Laser Ranging-Imager Sensor (ASLRIS) is a new generation of remote sensing and mapping system for providing 3D geosciences information. The system integrates the laser altimeter, IR imager, Differential Global Positioning System (DGPS) and Inertial Reference System (INS), by which Digital Elevation Model (DEM) and Georeferenced Image (GI) can be generated quickly and effectively without ground control point. The scanning laser rangefinder and the passive infrared scanning imager share the telescope and the scanning mirror. A suitable optical scanning mode is important to satisfy the demand of high-speed scanning and high-resolution laser ground sampling with limited repetitive rate of laser. The optical scanning of conical mode is studied emphatically comparing to the linear optical scanning mode in this paper, which two have been applied to the ASLRIS. The configuration, fundamental, specification and character of conical scanning technology are analyzed respectively. The principles to harmonize the conditions among scanning rate, optical aperture, scanning efficiency, platform flight height and repetitive rate of laser are specially studied. Finally the field test results of the ASLRIS are given.