Objective We aimed to summarize the clinical characteristics of floating thrombus in the inferior vena cava (IVC). Methods From January 2014 to June 2019, four patients with floating thrombus in the IVC were admitted to our hospital and underwent intracavitary therapy. Diagnosis, therapy, and clinical characteristics of floating thrombus were summarized. Results Three patients presented with pulmonary embolism. Three of the patients had a floating thrombus discovered by inferior venacavography and one was found by contrast-enhanced computed tomography. Two patients had deep venous thrombosis in the lower extremities. One patient had a double IVC, one had left iliac vein compression syndrome, and one had right renal phlebothrombosis. The four patients underwent implantation of a temporary IVC filter and were treated with anti-coagulation, debulking, and thrombolysis. All four patients achieved satisfactory results. Conclusions Floating thrombus in the IVC is often caused by spread of branch vein thrombosis, and is more likely to lead to pulmonary embolism. Anti-coagulant therapy and debulking under the protection of filters can achieve satisfactory clinical results.