Today ultrasonic power technique is consider a mandatory technique which is always entered in many processes such as in metal and plastic welding to overcomes many issues, with aided of applying force (pressure) and supplied high frequency vibration, a solid-state weld can be generated by ultrasonic metal welding technique. That give a technique the ability to join not only a small components, whereas also to join thicker specimens, depend on a proper control of matching welding conditions. Therefore a welding performance can be study and compared after designed welding horn to resonance at frequencies of 20 kHz and 40 kHz. The analyses of the designed horn are completed through use a vibration mathematical expressions, modal and harmonic analyses to ensure the weldability due to applying ultrasonic power to the working area and also to compare the performance of joint at using two resonance frequencies of 20 kHz and 40 kHz. The dimensions of the horns were determined to match the selected resonance frequencies, which the lengths were calculated as 132 mm and 66 mm respectively. The analysis of the exciting modal indicates that the axial vibration modes of 19,584Hz and 39,794Hz are obtained in 10th mode, while the two frequency values are recorded 19,600 Hz and 39,800 Hz from the frequency response of the two horns. The weld strength between Al and Cu specimens with a thickness 0.5 mm were evaluated using tensile test, which the analyses were obtained under using different welding pressure and varied amplitudes. The results were recorded within exciting a horn with two different resonance frequencies, show the enhancement of weld strength and quality through control of stepping amplitude, the enhancement means obtain good strength of the weld, reduce sticking horn to specimen, and lower specimen marking.