A COT control circuit used for realizing current sharing in multi-phase DC-DC converter. The multi-phase DC-DC converter has N switching circuits, N controllers, and a trimming current generator receiving N switching voltage signals of the N switching circuits to generate N trimming current signals. The N trimming current signals are respectively sent to the N controllers to regulate on time of at least one controllable switch of each of the N switching circuits so as to finally realize current sharing in the multi-phase circuits.