The invention provides a cutting mechanism for a steel cutting device and convenient to detach and maintain. The cutting mechanism comprises a cutting device base, the upper end face of the cutting device base is fixedly connected with a cutting platform through supporting pillars which are symmetrically arranged, the cutting platform is provided with an MAM-200 controller, and the MAM-200 controller is electrically connected with a power source; and the two ends, close to the edge, of the cutting platform are symmetrically and detachably provided with steel clamping devices, two sets of electric sliding channels driven by brushless direct-current servo motors are arranged between the two sets of steel clamping devices in the manner of being symmetrical about the center line of the cutting platform, the brushless direct-current servo motors are electrically connected with the MAM-200 controller, and the lower segments of the electric sliding channels are detachably installed on the cutting platform through electric sliding channel fixing pieces. All key cutting mechanism bodies and cutting-assisted mechanisms can be steadily connected with or safely detached from the cutting device, and the effect that detaching, transport and installation are all convenient to perform is achieved.