A GOA signal determining circuit and method thereof, gate driver circuit, and display device are provided. The GOA signal determining circuit is connected to an input end of a GOA unit, at least two clock signal ends of the GOA unit, and a control end of a reset unit of a PU node in the GOA unit. The GOA signal determining circuit detects a signal of the input end of the GOA unit and a signal of the at least two clock signal ends of the GOA unit, and outputs a control signal to the reset unit of the PU node to control the reset unit to output a reset signal to the PU node to turn off an output transistor of the GOA unit, upon determining both of the signal of the input end and the signal of the at least two clock signal ends are abnormal.