Abstract: The research results and main dynamic interaction analysis methods of small signal stability of AC/DC hybrid power systems with VSC-HVDC and VSC-MTDC in recent years, both china and abroad, were summarized in this paper. Concluded that challenges of small signal stability mechanism research of the complex AC/DC hybrid power system are as follows: 1) Traditional frequency analysis methods, represented by impedance method, can illustrate the dynamic interaction and mechanism in a simple hybrid system clearly, but cannot apply for the multiple input multiple output system; 2) The mechanism of complex hybrid power system small signal stability is hard to reveal because of the lack of methods. Finally, the research contexts in the future are indicated as: 1) Continue to improve the mechanism analysis method of single input single output hybrid power system, and enrich the inherent mechanism of small disturbance stability. 2) Put forward a suitable mechanism analysis method for multiple input multiple output, and reveal the inherent mechanism of the stability of complex hybrid power system.