Abstract: Voltage source converters (VSCs)-based AC/DC interconnected systems are increasingly studied and utilized due to their flexible access and efficient power conversion. However, the high proportion of renewable energy access and power electronics can cause stability issues, and the different power flow directions of the system can result in varying DC-side stability. In this paper, a DC-side admittance model of VSC is comprehensively established, taking into account factors such as bidirectional power flow, phase-locked loop (PLL), voltage and current control, and grid impedance. The DC-side admittance characteristics of VSC are analytically analyzed to reveal the origin of instability risk in the system. A DC voltage feedforward control method based on second-order differential loop is proposed to reshape the DC-side impedance of VSC for improving the stability of AC/DC interconnected system. Finally, a VSCs-based AC/DC interconnected system is constructed and emulated on the control-hardware-in-loop (CHIL) experimental platform to verify the accuracy of the analysis on the DC-side impedance characteristics and the effectiveness of the proposed impedance reshaping strategy.