A text conversion method and a text conversion system are provided. A term mapping table recording a term mapping relationship between a source language and a target language is provided. A tokenization process is performed on a paragraph in the source language to obtain tokenization results. The tokenization results are compared with the term mapping table to determine each source language term in the paragraph is belonging to a first type or a second type. The source language terms belonging to the first type are converted into corresponding target language terms according to the term mapping table. Regarding each source language term of the second type, one of multiple corresponding candidate target language terms is selected as the target language term according to a co-occurrence relevance of relevant terms, wherein each relevant term is constituted by one candidate target language term and words before and after that in the paragraph.