The invention discloses a cutting mechanism for a steel cutting device and with convenient disassembly and maintenance. The cutting mechanism comprise a cutting device base, a cutting platform is fixedly connected to the upper end face of the cutting device base through supporting columns arranged symmetrically, an MAM-200 controller is installed on the cutting platform, and the MAM-200 controlleris electrically connected to power supply. Steel clamping devices are symmetrically and detachably installed at the two ends, close to the side edge, of the cutting platform, two sets of electric slides driven by a brushless direct current servo motor are symmetrically arranged about the center line of the cutting platform between the two groups of steel clamping devices, the brushless direct current servo motor and the MAM-200 controller are electrically connected, and the lower sections of the electric slides are detachably installed on the cutting platform through electric slide fixing pieces. Each key cutting mechanism body and auxiliary cutting mechanism of the cutting mechanism can be firmly connected with the cutting device or be disassembled safely to achieve the effect of convenient disassembly, transportation and installation.