A light detection and ranging system comprises an optical transmitter for beam scanning on a scan region, and receiving reflected light from the scan region; and an optical receiver for directing the reflected light for signal conversion. The optical transmitter includes a beam refractive unit including optical refractive devices, rotatably disposed about a rotation axis, for directing a collimated laser beam from a first optical path towards a direction depending on rotation angles of the optical refractive devices; and a motion unit for actuating relative motion of the optical refractive devices so as to perform beam scanning towards directions on the scan region. The optical receiver includes an off-axis reflective unit, disposed in the first optical path, for directing the reflected light towards a second optical path; and a light detection unit, disposed in the second optical path, for performing signal conversion on the reflected light.