Aiming at the problem that the traditional protection gap can not extinguish the electric arc quickly and the trip rate of the line is high， this paper studies and designs the electromagnetic arc extinguishing air cannon. The device uses the electromagnetic piston theory to eject high-speed air masses. The high-speed air mass can impact the arc， take away the heat of the arc and draw the arc fine， enhancing the removing-free effect of the arc and forcing it to be extinguished quickly. And the spring mechanism installed at the piston end of theelectromagnetic arc extinguishing air cannon can automatically reset the piston after the electric arc extinguishing and be ready for the next time. According to the finite element method simulation， the arc can be drawn to 1/8 of its original thickness and the electric arc center temperature can be reduced to 1/3 within 16 msdue to the installation of the protection gap of electromagnetic arcing air cannon， which significantly enhances the removing free effect and forces the arc to be extinguished quickly. Therefore， the electromagnetic arc extinguishing air cannon has a stronger extinguishing ability and certain self-reliance， which can effectively reduce the lightning trip-out rate and improve power quality.