Abstract: OBJECTIVE To analyze and intervene the abnormal increase of the INR of warfarin in a patient with cerebral infarction complicated with atrial fibrillation, and to discuss the individual pharmacological service effect of clinical pharmacists in anticoagulant therapy. METHODS By participating in patients of cerebral infarction with atrial fibrillation with drug treatment options, analyzing INR increased abnormally, the clinical pharmacist explored the impact on pharmacokinetics and pharmacodynamics of warfarin and the mechanism affecting warfarin anticoagulation by drug interactions and disease state. RESULTS Cefoperidol sodium sulbactam sodium and Danhong injection were the drug factors enchancing the effect of warfarin anticoagyulation, and abnormal liver function was an other factor to aggravate this effect. CONCLUSION To the complexity of drug therapy in elderly patients of cerebral infarction with atrial fibrillation, the clinical pharmacist should carry out individualized pharmaceutical care, and focus on the interaction between Chinese and Western medicine, is beneficial to promote the rational use of drug, and ensure patients' safety.