A threshold voltage detection circuit for OLED display device includes a multiplexer connected between a detection IC and each of multiple sub-pixel driver circuits of a pixel driver unit. A second DC signal having first and second levels with the first level smaller than the detection control signal and the second level larger than the detection control signal is fed to each of the sub-pixel driver circuits, such that during detection of threshold of a driver TFT, the second DC signal is switched to the second level and during detection of threshold of an OLED, the second DC signal is switched to the first level and a data signal is set at the same level as the detection control signal to achieve detection of the threshold voltages of the OLED and driver TFT of each sub-pixel driver circuit.