arm's-length method: 独立企业交易法

 arm's length price: 独立企业间交易价格

 那么arm's length trade的意思应该就是“独立企业间贸易”，说白了就是企业内贸易，而这中企业间贸易和intrafirm trade 之间的区别，可能就是通过跨国公司等方式实现。

 arm's length price: 公平价格

arm's-length trade 公平贸易?

内部交易

arm's-length 手臂的长度

就是在自己的范围内，内部了

In the global business environment today, it is not unusual for subsidiaries of larger companies to conduct business transactions with one another, as if they are not all part of the same corporate family. When two companies that are affiliated by a connection through a parent company, the type of business they transact is often referred to as an arm’s length transaction. The price per unit that is extended for the items bought and sold is referred to as an arm’s length price. Here is some background on how the concept of an arm’s length price works, and why it is considered important.

还是看看正宗的解释吧