QDII (Qualification System for Overseas Investment of Domestic Institutional Investors) is an expedient measure to open the mainland capital market to the outside world under foreign exchange control. Domestic investors are allowed to invest in overseas capital markets when capital projects are not fully opened.

QDII means that mainland residents will be allowed to invest in overseas capital markets with foreign exchange. At present, most of them will invest in the Hong Kong capital market. Therefore, it is greatly influenced by the Hang Seng Index.