In allusion to the current situation that there is not yet mathematic model of describing the submerged arc welding system accurately, the mathematical model is established on the basis of mechanism modeling. Welding wire voltage drop son model, molten drop voltage son model and electric arc voltage drop son moder are established, which are regarded as the theoretical basis of the theoretical basis of the submerged arc welding system to control electric arc. And the corresponding variable speed wire control scheme is proposed according to the established model. By the control system simulation, it proves that the control scheme can maintain the stability between the wire feeding speed change and welding electric arc in the submerged arc welding process.