The report is about the patent linkage system in APEC economies. As a result of comprehensive research and survey across APEC economies, performed by the project under IPEG 04 2021T, the report identifies the concept and key elements of patent linkage system. On the basis of these key elements, the report attempts comparative analysis on various types of patent linkage system in APEC economies. Consequently, there are some differences in the way of introducing or operating patent linkage system between APEC economies. In this regard, the report shows that respective APEC economies need to take consideration of their own suitable regimes on patent linkage and pursue gradual cooperation in the field of intellectual property.