A threshold voltage sensing circuit applied in a display panel includes a first sensor and a second sensor. The first sensor positioned in the display panel receives an operation signal at a regular time point after start-up and continuously receives multiple driving signals which are the same as those received by the pixel circuits of the display panel and outputs a first output voltage accordingly. The second sensor positioned in the display panel receives the driving signals at a regular time point after start-up and outputs a second output voltage accordingly. When the voltage difference between the first output voltage and the second output voltage is beyond a variation standard, the low level of the gate voltage of the pixel circuit is adjusted.