A novel ultrasonic welding technique is proposed and the apparatus based on it is produced accordingly. The effects of weld technology on the strength have been discussed when evaluating with identical kind of polymers. According to the results, the protruded length and the surface roughness give poor effects on the welding strength. The higher welding stress and shorter welding time are more effective. There is an optimal welding stress in this method because the welding strength can be lower when the stress turns too strong. Moreover, the non-welded areas and the air bubble of the interface have given powerful effects to the strength. It is considered that the ultrasonic welding technique and the apparatus are quite effective to the weld process between polymer materials. POLYM. ENG. SCI., 49:1755-1759, 2009. (C) 2009 Society of Plastics Engineers