In this study, composite electroplating technique is used to fabricate the diamond-added copper (DAC) heat spreader for UV LED applications. Thermal dissipation characteristic and optical performance are improved as the composite DAC heat spreader adoption. The low thermal resistance of 18.4 K/W with UV LED using DAC heat spreader was measured. Surface temperature of UV LED using the DAC heat spreader is 45.32°C (at 350 mA injecting current), which is lower than those of LEDs using pure copper heat spreader (50.11°C) and only sapphire substrate (62.49°C). The thermal diffusivity of the DAC is 0.7179 cm2/s measurement by laser flash method. Output power and power efficiency of UV LEDs are also enhanced to 71.81 mW and 4.32%, respectively, at 350 mA injection current. The optimal structure design and materials fabrication will be discussed.