The United States is a country without foreign exchange control, so you can't exchange dollars in the United States through formal channels. You should change it in China in advance. Chinese in the United States will also accept that you pay US dollars for your own travel and tour groups, and are not particularly willing to pay RMB. The United States Customs stipulates that you can usually bring $5,000 online, and more needs to be declared. It is recommended that you bring $ 1000-$ 1500 in cash to pay for the extra self-funded items and other meals and consumption of the tour group. First, open a credit card or UnionPay card in China and deposit a certain amount of US dollars for shopping. It all depends on your personal shopping desire and shopping ability, and others don't know.