Hard brittle materials are widely continuously applied in aerospace and other fields, drilling micro deep holes whose surface morphology damage is less has been one of difficult technical problems in the manufacturing field. To drill the micro deep holes was explored by the ultrasonic Magneto-Rheological Fluids(MRF) composite drilling, and the MRF ultrasonic composite drilling rules were revealed through establishing material removal model. It is verified that the drilling effect of surface quality of micro holes is well improved by experiments in using the method.