An optical testing system combining projection and schlieren techniques. In the testing system, a combination of optical characteristics is generated by moving two lenses (2) and (4), so as to separately form a projection telephoto optical system and a schlieren photographic optical system, thereby achieving an optical system and device having the functions of both a projection optical system and a schlieren optical system. The invention enables two devices having different optical testing functions based on two different optical principles to be implemented in a single device, greatly saving design and manufacturing costs of the testing device and increasing the functions thereof, facilitating testing performance, and reducing the space occupied by the testing device.