Disclosed is a black level cancellation method, comprising: receiving a first level signal and a second level signal that are outputted by an effective pixel unit; starting first counting when receiving the first level signal and a ramp signal, and stopping the first counting when the amplitude of the ramp signal is equal to that of the first level signal, to obtain a first count value; performing timing when receiving the second level signal and the ramp signal, starting second counting after delaying for the preset quantity of clock periods, and stopping the second counting when the amplitude of the ramp signal is equal to that of the second level signal, to obtain a second count value, wherein the preset quantity is a black level value of a non-luminous pixel unit; and obtaining a digital signal according to the first count value and the second count value. The method cancels a black level during conversion of a second level signal, and saves the time needed by subtracting a black level value from an analysis result of an effective pixel unit in a digital circuit.