Type Ⅱ heparin-induced thrombocytopenia （HIT） is a life-threatening adverse drug reaction initiated by heparin administration. We described a rare case of LMWH-induced HIT complicated with proven pulmonary embolism （PE） in a 75-year-old male patient who hospitalized with diagnose of right knee osteoarthritis and was underwent total knee arthroplasty. The patient was successfully treated with argatroban. Early recognition and timely alternative therapy are of great importance in the treatment of this severe disorder.