The present invention discloses an external compensation GOA circuit and a display panel. By adding a random detection signal output branch, a first output waveform of a scan signal line fulfilling normal driving is outputted in a normal time, and a second output waveform of the scan signal line fulfilling blanking time random detection is outputted in a blanking time, such that randomly detecting a threshold voltage of the drive transistor by using the blanking time of the scan signal can be achieved to further achieve external real time compensation of the threshold voltage shift, enhance uniformity of screen image display, and improve a lifespan of the display panel.