The present disclosure provides an OLED package structure, OLED device, display device and method for fabricating OLED package structure. The OLED package structure includes a substrate, a cover plate and a first sealant layer. The substrate, the cover plate and the first sealant layer together delimiting a sealed space. The OLED package structure further includes a functional sealant layer formed by filling the sealed space with a functional sealant, and a second sealant layer formed by a second sealant disposed between the substrate and the functional sealant layer. The second sealant has a density less than a density of the functional sealant.