An improved system for monitoring clock duty cycles, comprising: a first monitoring circuit configured to record a first quantity of high levels of the monitored clock signal sampled by a first random clock signal; a second monitoring circuit configured to record a second quantity of high levels of the monitored clock signal sampled by a second random clock signal, wherein the phase of the second random clock is adjusted by a second adjustment degree based on a first clock; a third monitoring circuit configured to record a third quantity of high levels of the monitored clock signal sampled by a third random clock signal, wherein the phase of the third random clock is the reverse of that of the first random clock; and a calculation module configured to determine a duty cycle of the monitored clock based on the first quantity, the second quantity, and the third quantity.