Performance Monitor Counter(PMC)-based and circuit signal-based approaches are the two primary methodologies for online power estimation of processors. PMC-based methods will not bring hardware overhead, but the observation granularity is too large to be applied to fine-grained power management strategies. Meanwhile, signal-based methods bring high hardware overhead, and current power management strategies cannot effectively utilize clock-level precision. In this paper, we propose Power Abstract Counter(PAC). This counter records the change times of circuit signal closely related to the processor’s power consumption. We also developed an online power estimation method based on PAC. This method combines the advantages of PMC-based and signal-based methods. It can estimate the processor’s power at a smaller observation granularity and has a low hardware overhead. We validate the approach on the Loongson GS364 processor. The results show that using 16 PACs can achieve an estimation error of less than 1% within a granularity of 512 cycles.