A fast iris diaphragm driven by symmetric electromagnet comprises: two symmetric one-sided diaphragms, each of which comprises a diaphragm blade, a first-level support, a secondary support, two fixing seats, two magnetism conductive plates, four permanent magnets, two guide bars, a drive coil plate and a photo-electric switch circuit board; and a drive control system, comprising a magnetic field formed by a photo-electric switch circuit board, a drive coil plate and four permanent magnets, and a drive control circuit; the drive control circuit converts the input control signal into the large power signal to drive the drive coil plate to push the first-level support to move; the first-level support drives the diaphragm blade to move to realize opening and closing of the diaphragm; the feedback signal transmitted back by the photo-electric switch circuit board is collected for judging the opening and closing situations of the diaphragm blade to control the effective opening and closing of the diaphragm blade. The fast iris diaphragm driven by symmetric electromagnet can realize the switching of the light transmission quantity of the optical system, and is applied to the occasions such as strong light protection of imaging device and changing of focus depth of the optical system, and also realizes the shutter effect or optical modulation.