A circuit and a method for controlling multi-channel power are disclosed. The method includes: according to a channel selection signal in the previous clock cycle, select one channel signal from the received at least one channel signal in the previous clock cycle; according to an amplification factor control signal in the previous clock cycle, amplify the selected one channel signal to acquire a first signal; perform A/D conversion on the first signal to acquire a second signal; and according to the second signal, generate an amplification factor control signal in the next clock cycle, so that according to the amplification multiple control signal in the next clock cycle, amplify the selected one channel signal in the next clock cycle when the next clock cycle comes. The scheme can be used to detect the multi-channel optical power and its circuit implementation is simple.