Abstract: Objective The aim is to investigate effect of segmented ultrasonic welding amplitude on performance and microstructure of wire harness-terminal joints. Methods Taking EVR 50 square shielded high-voltage wire as a research object, ultrasonic welding experiments were conducted on wire harnesses with a single variable. Taking segmental welding amplitude as a variable, static mechanical properties and microstructure of welded joints were systematically investigated by tensile tests, conductivity tests and scanning electron microscope experiments. Results The results show that when welding amplitude is 60%/60%, the mean load of welded joints is 3.5 kN and resistance of welded joints is 43 μΩ. When welding amplitude is 80%/80%, the mean load of welded joints is 4.5 kN and resistance of welded joints is 42 μΩ. When welding amplitude is 80%/60%, the mean load of welded joints is 3.4 kN and resistance of welded joints is 43 μΩ. When welding amplitude is 60%/80%, the mean load of welded joints is 4.9 kN and resistance of welded joints is 41 μΩ. Conclusion Load of welded joints increases with welding amplitude, and mechanical properties of welded joints are better in the second half of welding process than those in the first half of welding process, and it is found that the connection between wire harness and terminal is gradually realized inward from the direction of welding tool head.