Abstract: With the rapid development and application of HVDC transmission technology, more and more AC/DC hybrid power systems have been parallel, with the ever increasing coupling influence between AC system and DC system imposed. In this paper, the stability characteristics of AC/DC parallel power grid in CSG was analyzed in detail. Besides, the potential risks induced by both AC faults or DC faults that can lead to the instability of the main CSG grid have also been elaborated. Then the evolutionary process of complex instability caused by interaction of AC and DC power systems was investigated. Based on the above, the necessity of asynchronous interconnection between Yunnan Power Grid and the rest of CSG was illustrated. Finally, the asynchronous interconnection scheme based on HVDC transmission technology was discussed, which can provide technical support for safe and stable operation of AC/DC parallel power grids.