Abstract: Spatter experiments of CO2 arc welding with different parameters arc conducted under the conditions of without magnetic field,with a longitudinal magnetic field.The experiment results show that the longitudinal magnetic field could control the short-circuiting transfer spatter with in certain welding parametem and obtain good technological effect.The good effect could be obtained in a certain longitudinal magnetic field scope.The causes are discussed,and the section dimensions and the formation of the welding seams are also investigated.