The invention relates to a micro and fine machining method for a material difficult to machine and a machining system, belonging to the technical field of composite, precise, micro, fine and special machining. In the method and the machining system for implementing the method disclosed by the invention, ultrasonic modulation, low-voltage discharge and electrolysis are effectively compounded, a micro and fine discharge-electrolysis function is organically combined with ultrasonic frequency vibration identical frequency and synchronization, and discharge of machining products and circular update of a working fluid are realized under the actions of ultrasonic cavitation and spark discharge explosive force, so that a gap machining process is improved effectively, localized machining performance is enhanced, machining accuracy and surface quality can be further enhanced while high machining efficiency is achieved, machining can be realized in a static fluid simultaneously, and complex pressure flow and circular supply of the working fluid to the system is not required; and during processing, contact of the workpiece with an electrode under a certain constant pressure is kept, continuous and stepless micro pressure adjustment can be performed by using a magnetic adjusting mechanism, and a precision stable-speed micro feeding system necessary for electrolytic machining and a servo feeding system necessary for electric spark machining are not required, so that the equipment research cost can be reduced greatly.