Truly, the best way to be able to conduct business using English is just to become fluent in general English.
Almost all of the words and grammatical concepts that business people use are identical to those used by people in daily life, with a few new vocabulary words thrown in that a fluent speaker would be able to pick up quickly. After all, native English speakers do not need to study business English because they already speak normal English well enough to easily learn new terms as they occur in their jobs. Office culture and terminology varies from job to job as well, so that's a reason that it's better to just become excellent at general English than to study business-related terms themselves.
That said, if you really insist on studying business-related English vocabulary, check out this resource from the BBC.
October 9, 2012
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Chinese (Mandarin), Chinese (Cantonese), Chinese (Other), English