Abstract: Magnetic pulse-assisted semi-solid brazing made full use of the characteristics and combined advantages of each process to realize the effective connection of heterogeneous Cu/Al tubes. Aiming at the problems such as uneven removal effect of interfacial oxide film and significant difference of diffused layer depth when connecting Cu and Al tubes with traditional magnetic field-shaper. A new type of multi-seam field-shaper was designed in this paper. Through the combination of numerical simulation and experimental study, the effects of the number of seams and the length of seams on the welding process were investigated during magnetic pulse-assisted semi-solid brazing of small-diameter heterogeneous Cu/Al tubes. The results showed that when the number of seams was 3, and the length of the short seams was 0.25 ~ 0.5 times of the wall thickness in the field-shaper, the circumferential electromagnetic force distribution of the tube was significantly improved. The shear stress of the filler metal and the corresponding shear rheological was changed more evenly and fully. The oxide film was removed more thoroughly in the lap area, and the element diffusion was promoted. The novel multi-seam field-shaper was beneficial to form an effective metallurgical bonding at the interface between the substrate and the brazing seam, and improved the interface quality and mechanical properties of the joint.