The growing concern regarding electromagnetic interference (EMI) has prompted the development of research focusing on the enhancement of power density in products through the integration of EMI filters. In comparison with passive EMI filters (PEF), active EMI filters (AEF) offer distinct advantages, including high power density and compact size, which facilitates their broad application prospects. This paper presents a theoretical analysis of the filtering performance and stability of the voltage-sampling current compensation (VSCC) AEF from an overall system perspective. Initially, the stability of the differential mode noise suppression AEF system is analysed, and a comprehensive model of the three circuits in the VSCC AEF is constructed. Secondly, expressions for the low frequency and high frequency loop gains, crossover frequencies and gain margins are given; the effects of various parameters on the stability are analysed, and the effects of different compensation methods on the loop gains are also shown. Finally, the results are validated in a 400 W DC/DC buck converter. Experimental results demonstrate that the noise attenuation can achieve over 35dB within the frequency range of 100 kHz to 10 MHz, and the experimental outcomes align closely with the theoretical data.