The invention provides a large-aperture totally-reflective optical synthetic aperture imaging system, which solves the problem that the traditional single large-aperture optical system is difficult to process and manufacture and the problem that some simple synthetic aperture imaging systems cannot achieve the desired system indexes during practice. The large-aperture totally-reflective optical synthetic aperture imaging system is provided with two sub-telescopes, wherein each afocal sub-telescope consists of a remote control (RC) system, a first planar reflector and a first concave reflectorwhich are arranged sequentially along with a light incidence direction; the RC system is confocal with the first concave reflector; the first planar reflector is positioned on a focal plane; an optical delay line is a second planar reflector group, which is arranged between the two afocal sub-telescopes spatially; and a beam synthetic mirror consists of four reflectors arranged in an aperture off-axis mode. In the large-aperture totally-reflective optical synthetic aperture imaging system, two small-aperture systems with the same structure are designed, so that modularized production and detection are realized, difficulties in processing and manufacturing of the system are reduced, volume and weight of the whole system are greatly reduced, and development cost is greatly reduce.