It is critical to understand the dominant recombination mechanisms of thin film solar cells for further improving their performance. The dominant recombination paths of CdTe solar cells with MgxZn1.xO (MZO), MZO/CdS and MZO/CdS/CdSe buffer layers were investigated by temperature-dependent current-voltage (JVT) characterization both in light and dark, with traditional CdS/CdTe devices as a reference. The devices with MZO or MZO/CdS buffer layers are confirmed to be dominated by interface recombination, which leads to poor performance of devices. Compared to devices with traditional CdS buffer layers which are dominated by bulk recombination, the devices with MZO/CdS/CdSe buffer layer exhibit the same dominant recombination path but superior performance. It demonstrates that MZO/CdS/CdSe can be a promising composite buffer layer.