Illegal, unreported and unregulated(IUU) fishing is a serious global problem, and IUU fishing practices include the violation of national and international laws, misreport of catches quotas or species, escape from national or international fishery organization control, etc. IUU fishing jeopardizes the marine ecosystem, food safety, fishermen livelihood, also causes tax evasion, and even transnational crime, such as slavery at sea, especially man and child trafficking. To analyze IUU fishing problem, it's not enough just to know about IUU fishing places, we should also master how IUU catches come into market in the end. From this perspective, this paper takes the main wild-catch seafood exporting from China to USA for example. To analyze China's IUU fishing situation, first of all, through the quantification in 2014 China's main export wild-catch seafood(pollock, salmon, crab) to USA, according to the volume of IUU fishing in proportion, and comparing with the main exporting countries, we can find that the IUU catch scale is large exporting into the United States. Then taking the supply chain as the breakthrough point, we can summarize the reasons as follows:First, the supply chain of wild-catch seafood lacks transparency and traceability. Second, all three species undergo transshipping from Russia and are processed in China before re-export to the United States and all three have been linked to high levels of illegal fishing. When analyzing the policies in USA combating IUU fishing in recent years, especially the U.S. Seafood Traceability Program, it takes trade control as mechanism to combat IUU, and it's also a great test to the traceability of seafood from our country. Finally, considering the latest international instrument combating IUU fishing, i.e. Voluntary Guidelines for Flag State Performance, we can not only learn some specific measures about strengthening sanctions against IUU fishing as legislation, but it's also a test for our country combating in IUU fishing.