Facial expression was an important communication methods. In oriental medicine, according to the emotion the face has changed shape and difference occurs in physiology and pathology. To verify such a theory, we studied the correlation between emotional facial expressions and meridian and collateral flow. The facial region divided by meridian, outer brow was Gallbladder meridian, inner brow was Bladder meridian, medial canthus was Bladder meridian, lateral canthus was Gallbladder meridian, upper eyelid was Bladder meridian, lower eyelid was Stomach meridian, central cheeks was Stomach meridian, lateral cheeks was Small intestine meridian, upper and lower lips, lip corner, chin were Small and Large intestine meridian. Meridian and collateral associated with happiness was six. This proves happiness is a high importance on facial expression. Meridian and collateral associated with anger was five. Meridian and Collateral associated with fear and sadness was four. This shows fear and sadness are a low importance on facial expression than different emotion. Based on yang meridian which originally descending flow in the body, the ratio of anterograde and retrograde were happiness 3:4, angry 2:5, sadness 5:3, fear 4:1. Based on face of the meridian flow, the ratio of anterograde and retrograde were happiness 5:2, angry 3:4, sadness 3:5, fear 4:1. We found out that practical meridian and collateral flow change by emotion does not correspond to the expected meridian and collateral flow change by emotion.