Metaphor, as a cognitive mechanism, plays a key role in the translation process, giving rise to the Metaphor Translation Theory. This paper attempts to explore the thinking approach and operational mechanism behind English translation of traditional Chinese medicine (TCM) discourse based on the Metaphor Translation Theory. The results demonstrate that target language (English translation) creation can be interpreted as a metaphorical process whereby the translator pursues cross-domain mapping, searching or establishing resemblance, relation, and correspondence between source language (TCM discourse) and target language variables across slots, relations, attributes and knowledge. This is done with comprehensive consideration of factors such as highlighting, coherence, cultural differences, and innovative spirit, in an attempt to identify appropriate translation methods that balance retaining Chinese cultural elements and target reader acceptance.