Abstract: The introduction of invasive harmful marine species into new environments has been identified as one of the four greatest threats to the global ocean ecosystems.The ship ballast water is the main way for the transfer of aquatic invasive organisms.In this paper,the relationship between the foreign trade cargo loading capacity of all above scale ports and ballast water input of entry ships was analyzed,based on the information of foreign trade and the import and export of goods published by the State Department of Transportation and the State General Administration of Customs.Moreover,an estimation model for entry ship's ballast water input at Chinese ports was established.Results show that more than 267 million tons of entry ship's ballast water from the other global ports was discharged at Chinese ports per year.It is a huge threat to the ecological environment of Chinese ports area.This research provides both a background information estimation method and basis for the risk assessment,management and zonation of the non-indigenous marine organism invasion in China.