A　digital　tongue　image　analysis　instrument　(TIAI)　based　on　computer　for　Traditional　Chinese　Medicine　is　introduced.　Some　of　the　key　techniques,　including　the　image　acquiring　condition　and　method,　the　evaluation　of　tongue　characters,　and　the　management　of　tongue　image　data,　are　discussed　as　well.　TIAI　can　provide　a　non-invasive,　quantitative,　and　objective　analysis　approach　and　enhance　the　theory　level　and　practical　ability　of　the　Traditional　Chinese　tongue　diagnosis.