An organic light-emitting diode (OLED) display panel, a manufacturing method thereof, and an OLED display device are provided. At least one of a substrate or a backplate in the OLED display panel has a reduced thickness, thereby increasing light transmittance of an electronic element area. Furthermore, an area where a camera lens is disposed can display normally and an under-display camera can be realized without defining a hole. Therefore, a screen-to-body ratio is increased, and a technical problem is solved: in conventional OLED display panels, the hole needs to be defined on the area where the camera lens is disposed, leading to a display effect being affected.