Abstract: Studies factors affecting functions of demulsification on mixing demulsifiers. Through orthogonal and single factor tests, optimum conditions of mixing TA 1031 and RI 01 were obtained, viz.: 65 ℃, 2∶1, at 80 mg·L -1 and 90 min. Under these conditions, ratio of dewatering of crude oil can reach as high as 98 5%. The mixed demulsitier increased the dewatering efficiency to an extent of 14%～16%.