The paper studied the change rule of the forepart of initial solidified shell, cross-section structure and elements distribution of horizontal continuous casting Zn-Cu alloy billets under electromagnetic field. The results show that the forepart position changes with the casting speed, pouring temperature and current intensity. Among these parameters, casting speed plays the most important role. It is only adjusting the corresponding casting speed according to the current strength and the pouring temperature that can improve the structure and reduce segregation. The forepart moves backwards by enhancing the current and the casting speeds. When the liquid-solid interface locates in the interspace between the cooling water jacket and the electromagnetic stirrer, the inverse segregation of Cu can be effectively suppressed. Electromagnetic field removes the nonuniform cross-section structures and the difference between the final solidification area and billet geometric center, and refines the dendrite structure. Stirring does not completely eliminate the deep gray dendritic copper rich phases in the edge or center of the billets, instead of slightly larger dendrite sizes and the small edge-center structure difference. When casting speed and current intensity is 3 m/h and 100 A, respectively, the most uniform and refined structure is obtained, while no obvious change can be seen for other currents and frequencies. The addition of Ti cannot refine the billet structure or eliminate the inverse segregation, but make the melt sticky with poor fluidity