An OLED display panel and a manufacturing method thereof, and an OLED display device are disclosed. The OLED display panel includes a base substrate; a first film layer and a second film layer, sequentially provided on the base substrate, a first via-hole penetrating through the first film layer being provided in the first film layer, a second via-hole penetrating through the second film layer being provided in the second film layer at a position corresponding to the first via-hole, the second via-hole being in communication with the first via-hole, and the first film layer and the second film layer form a first step at a position of the second via-hole; and a connection wire, provided in both the first via-hole and the second via-hole and overlying the first step.