An OLED display panel and a fabrication method thereof, and a display device are disclosed. The OLED display panel comprises: an array substrate and a package cover plate disposed opposite to each other, and an OLED layer which is formed on a surface of the array substrate facing the package cover plate and comprises a plurality of OLEDs. The OLED display panel further comprises: a first thin film packaging layer, covering the OLED layer and bonded to the array substrate; a color filter layer, provided on a side of the first thin film packaging layer facing the package cover plate; and a bonding adhesive, filled between the array substrate and the package cover plate to bond the array substrate and the package cover plate, the bonding adhesive covering the color filter layer and the first thin film packaging layer.