Optical characteristics including the radiant flux and viewing angle of UV LEDs were investigated according to both silicone encapsulants with different refractive indexes and lens shapes. Lead frame was fabricated using the enhanced heat dissipation characteristics with a heat slug structure and the reflector based on EMC(Epoxy Mold Compound) material. Four types of lens shapes were designed and their optical characteristics depending on the refractive index of silicone encapsulants were evaluated. The maximum radiant flux can be achieved when the height of lens are 1.32mm and 1.08mm for silicone encapsulants with low and high refractive indexes, respectively. Depending on the encapsulating method, the viewing angle changes from 148.9° to 130.2° for low refractive index and from 145.3° to 136.8° for high refractive index. As a result, it is found that the optical characteristics of UV LEDs can be controled through both encapsulating method and the refractive index of encapsulants.