The invention discloses a high-speed mechanical switch for alternating current and direct current high voltage. The high-speed mechanical switch comprises a double-head air cylinder assembly, a movable electrode assembly, a static electrode assembly, a fixed part, a lead guide and a plane calibration plate, wherein the double-head air cylinder assembly and the static electrode assembly are fixed on the plane calibration plate through the fixed part; the central symmetrical axes of the double-head air cylinder assembly, the movable electrode assembly and the static electrode assembly are collinear. The high-speed mechanical switch disclosed by the invention adopts a modularized design with a compact structure, and is convenient to detach, maintain, assemble and debug; millisecond-order electrical connection and isolation of a 0 to 20KV alternating current and direct current circuit can be realized under a complicated magnetic field environment; a rapid plug connector electrode, which iseasy to machine, is put into a guide pipe and is used for effectively carrying out dust prevention and water prevention on an electrode; the double-head air cylinder assembly can realize switching-on/off of two independent switches within one period, so that energy sources are effectively utilized; the function of a single-pole double-throw switch also can be finished; the high-speed mechanical switch has a wide application prospect in the technical field of high voltage, especially in the field of accelerators.