The embodiment of the invention relates to the liquid crystal display technology field, especially to a circuit of gate drive on array (GOA), a shift register and a display screen. The GOA circuit comprises a first thin film transistor (TFT), a second TFT, a third TFT, a fourth TFT, a capacitor and a drop-down module. The drop-down module, which is connected between a first clock signal input terminal, a second clock signal input terminal, a first node and an output terminal and is connected with a low level signal terminal, is used for maintaining the first node and the output terminal to be at a low level within non-working time of the GOA circuit of this row. According to the invention, functions of an input terminal and a reset terminal in the GOA circuit are designed to be symmetrical, so that the GOA circuit can realize bilateral scanning without changing charging and discharging characteristics of a node; and thus reliability and stability of the circuit are ensured.