Abstract: In the past decade, many resonance accidents have emerged in flexible high voltage direct current(HVDC) systems. In China, Nanhui project(a demonstration), Yu’E project, Zhangbei DC grid and some other flexible HVDC projects have all experienced wide-band resonance issues. These resonace accidents have different manifestations in different projects, but there are some common characteristics and differences: for example, similar mid-low frequency oscillations (frequency of tens of Hertz) have occurred on the DC side of the Xiamen and Yu’E projects converter stations, while Yu’E project and Zhangbei project have both experienced high-frequency oscillations of thousands of Hertz in the AC measurement of the converter stations after being connected to the AC power grid. In order to clarify the laws and characteristics of these oscillation accidents in domestic flexible direct current transmission projects, the typical approaches for investigating the root cause of resonances in the flexible HVDC are introduced firstly. Then, the resonances issues in several practical flexible HVDC projects are analyzed from the impedance view. Furthermore, several typical resonance suppression strategies and potential solutions for the flexible HVDC are introduced. Finally, the state-of-the-art of the wide-band resonances in VSC-HVDC is summarized and some suggestions for the future R&D of flexible HVDC system resonance issues are given.