An optical-mechanical scanning platform for terahertz imaging is designed and studied based on the single-channel 360-GHz radiometer. The fast scanning of 360-GHz Cassegrain antenna beam is realized through the rotation of a metal mirror with the inclination of 45-deg angle. An optical-mechanical scanning platform with fast 2D beam scanning is integrated into the 360-GHz terahertz wave imaging system. The imaging results show that the initial design goal of the imaging system is completed.