Scientific exchange and collaboration between the two largest economies in the world are now facing serious challenges,due to isolationist policies of the Trump administration.The USA has been the leading country in attracting inteational talents and in promoting scientific exchange and collaboration.The sudden change in the climate appears to be triggered by the USA-China trade conflict and the perceived threat of Chinas scientific and technological advancement to the US supremacy in the world.Under the disguise of national security,the Trump administration has ordered the Federal Bureau of Investigation to step up the surveillance and investigation on research activities of foreign-bo students,researchers and visiting scholars in US research institutions,targeting specifically those of Chinese origin,on the basis of a few isolated cases of alleged illegal transfer of intellectual property.