A 65-year-old patient was admitted to the hospital due to proptosis of the left eye accompanied with ophthalmodynia and toothache for two months. Ophthalmic examination revealed a palpable mass around the lateral orbit and temporal fossa, and maxillofacial CT suggested a malignant tumor invading the left orbital floor wall. One week later, the patient was diagnosed with left orbital cellulitis and septic shock due to peri-orbit redness, eyelid edema, chest tightness, nausea, vomiting, hypotension, and a marked increase in peripheral blood neutrophil count. The infection was well controlled after remission of shock, anti-infective therapy and surgical drainage. At 2 months after surgery, the surgical incision of the upper eyelid skin recovered well and the best corrected visual acuity of the left eye was 1.0.