原理很简单，当两个货币对的价差放大或缩小的时候一边做多一边做空，等两边价格运动到一定差价时，会盈利，这就是双货币套利。(The principle is very simple. When the price difference between two pairs of currencies is enlarged or narrowed, the two pairs of currencies will make profits when the price moves to a certain difference. This is called Double currency arbitrage.)