OLED display is a new generation of display to replace LCD. Liquid optically clear adhesive (LOCA) used for bonding between display components is one of the key materials of OLED. LOCA with high refractive index, high thermal conductivity and high stability is particularly important for OLED performance. In this paper, octavinylsesimiloxane polyhedral oligomer silsesquioxane (OvPOSS) was grafted into polyurethane acrylate (PUA) resin with good adhesion and optical properties by simple UV-initiated thiol-ene reaction. LOCA with high transparency and refractive index was prepared by using OvPOSS as the reinforcing filler and trimethylolpropane-tri (3-mercaptopropionate) (TTMP) as the crosslinking agent. Studies have shown that the prepared LOCA can be cured within 20 s of 365 nm UV irradiation, the curing time of which is much shorter than that of other commercial UV adhesives, with lower energy consumption. When the addition amount of OvPOSS is 7 wt%, compared with pure PUA, the refractive index is increased to 1.525, the thermal decomposition temperature Td5% is increased by 30 ℃, the glass transition temperature is increased by 5.3 ℃, and the thermal conductivity is increased from 0.0609 W·m-1·K-1 to 0.1710 W·m-1·K-1. At the same time, the adhesion strength is increased from 3.16 MPa to 3.48 MPa, the visible light transmittance can still reach more than 99% after 1440 h sunshine irradiation at room temperature, and the water absorption rate is only 0.52% after 3600 h immersion in water, which is lower than 0.70% (24 h) in available reports. All this suggests that the OvPOSS/PUA liquid optically clear adhesive has a great application prospect in the packaging of photoelectric devices.