The invention discloses a device and a method for realizing multi-beam pulse laser output employing a laser output mirror film control technology. The device comprises a front cavity mirror of a resonant cavity, an annular condenser cavity, a laser pumping source, a laser crystal rod, Q-switched crystal and a controlled coating laser output mirror, wherein the front cavity mirror of the resonant cavity and the controlled coating laser output mirror form the resonant cavity of a laser oscillator; laser emitted by the laser pumping source is condensed into the laser crystal rod through the annular condenser cavity; the laser crystal rod absorbs pump energy; oscillating laser is generated between the front cavity mirror of the resonant cavity and the controlled coating laser output mirror; the laser passes through the Q-switched crystal and then is modulated into a pulse form; and multi-beam laser is output outside the resonant cavity after passing through the controlled coating laser output mirror. According to the device and the method, multi-beam pulse laser output (N beams) is finally generated by multi-beam laser oscillation in the resonant cavity by a controlled coating technology, and is used for improving the ignition success rate and reliability of an engine.