Objective of the study was to evaluate the pain relief effect and the effectiveness in treating urinary retention in patients post transanal hemorrhoidal dearterialization (THD) by electro -acupuncture. 120 patients with internal hemorrhoid grade II, III, IV treated by THD in the Surgery Department, National Hospital of Traditional Medicine from February to August 2012, were randomly divided into 2 groups: study group using electro - acupuncture and control group using 20mg Felden 1M once a day when patients felt painful after surgery. All the patients have significantly lower VAS score after treatment (p 0.01). The Electro - acupuncture group had significant lower rate of pain recurrence and urinary retention than the Felden group (p 0.05). In conclusion, Electro - acupuncture has an analgesic effect and is effective in treating urinary retention effect in patients after hemorrhoid surgeries by THD.