Authors report a case of cystic tuberculosis of left olecranon in a 44 year-old woman, which mimicked the bone tumor at initial presentation. She complained mild discomfort in the left elbow over a month. On examination there were no local redness, swelling, tenderness and deformity. There was no limitation of left elbow motion. After open curettage of the lesion, bone tuberculosis was confirmed by histological study. Postoperative triple chemotherapy of 12 months (Rifamcpicin, ethambutal, INH) could cure the disease.