An organic light emitting diode (OLED) display panel is provided. The OLED display panel includes a substrate, a conductive layer, an active matrix pixel array and several thin film transistors (TFTs). The conductive layer having several openings is disposed above the substrate. The active matrix pixel array having several pixels is disposed above the conductive layer. Each pixel has a display region and a non-display region. The display regions correspond to the openings. The TFTs are correspondingly disposed inside the pixels and correspondingly positioned inside the non-display regions. Each TFT includes a channel layer, a source, a drain and a gate. The channel layer is disposed above the conductive layer. The source and the drain are disposed above channel layer and respectively contact with the two opposite sides of the channel layer. The gate is disposed above the channel layer and positioned between the source and the drain.