The horseshoe vortex generated in the attached part of a submarine could aggravate the vibration and noise of the submarine. The control mechanism of a vortex control baffle for the horseshoe vortex around the sail of a DARPA SUBOFF model is explored by the large eddy simulation (LES) model in this work. The variations of the distributions for streamwise vorticity, Q criterion and pressures are analyzed deeply. It is found that the arrangement of the vortex control baffle can interfere with the development process of horseshoe vortex. Due to the presence of the baffle, a strong reverse pressure gradient around the baffle would take place. Then a series of vortices are generated to weaken the intensity of the horseshoe vortex in the process of propagation and achieve the purpose of controlling the horseshoe vortex. The development characteristics of these vortices are discussed in detail. It is noted that the new induced vortex and the horseshoe vortex have opposite propagation direction, which would lead to the gradually decreasing intensity of the horseshoe vortex in the development process.