This study develops a precise evaluation methodology for current-compensated active EMI filters through noise injection principles and corresponding test system implementation. Furthermore, a novel common-mode current rejection ratio (CMCRR) metric is proposed to characterize the common-mode suppression capability. To identify key parameters influencing the consistency of common-mode suppression characteristics testing, the test system is modeled and analyzed. The accuracy of the test system hinges on the efficiency of the noise injection component, leading to a detailed model of the current injection probe, which is subsequently validated. Furthermore, a simplified model of the test system is established, revealing that the CMCRR of passive EMI filters are solely determined by their impedance parameters Z21 and Z22. The π-filter is employed to validate both the noise injection model and the simplified test system model. The results demonstrate that, across the frequency range of 100 kHz to 10 MHz, the maximum discrepancy between calculation and measurement results for both models remains within 3 dB. Finally, the practicality of the test system is demonstrated through the evaluation of the Vicor QPI21 active EMI filter.