OBJECTIVE： To discuss the role of clinical pharmacist participating in drug therapy for severe ulcerative colitis （UC） during late pregnancy. METHODS： Clinical pharmacists participated in the therapy for a UC patients during late pregnancy， assisted the doctors to optimize and improve drug therapy plan from antidiarrheal， anti-intestinal inflammation， regulating intestinal flora， recovering damaged mucosa； suggested regimen was as follows： montmorillonite powder 3 g， pr， qd， to avoid drug interaction； hydrocortisone 100 mg， ivgtt， bid to resist intestinal inflammation； prednisone 30 mg， po， qd+20 mg， po， qn， instead after symptom relieved； stopping taking Bifid triple viable capsules， supplementing Human serum albumin injection， Nutrients， Potassium chloride injection， Concentrated sodium chloride injection， etc. RESULTS： The suggestion provided by clinical pharmacists was adopted by doctors， and the patient was recovered. There was no significant difference in the intelligence development， body weight and height charge between born baby boy and infants with same month age. CONCLUSIONS： Clinical pharmacists assist physician to optimize and improve drug therapy plan to promote rational drug use in the clinic and guarantee the safety of drug use.