Deep vein thrombosis (DVT) is one of the common diseases in vascular surgery, with an incidence of about 1 per 1,000. the acute phase of DVT can cause progressive increase in venous obstruction due to the spread of thrombus, and even cause femoral cyanosis leading to limb necrosis and amputation, and free thrombus dislodgement can also lead to fatal pulmonary embolism. post-thombosis syndrome (PTS), which is the coexistence of venous reflux caused by proximal venous blockage and venous reflux caused by venous valve destruction, causing venous hypertension in the lower extremities and corresponding clinical manifestations, manifesting as swelling, varicose veins and even chronic ulcers in the affected limbs. It brings serious impact on the quality of life of patients. Currently, the treatment methods used for acute lower extremity DVT can be divided into two categories: traditional anticoagulation therapy and non-traditional therapy. ①Traditional treatment includes bed rest, elevation of the affected limb, wearing elastic stockings, and anticoagulation and systemic thrombolytic therapy. Anticoagulant drugs can prevent further formation of thrombus to a certain extent, but cannot remove the existing thrombus, and the therapeutic effect is limited, while the thrombolytic efficiency of systemic thrombolytic therapy is also low, so more than 50% of DVT patients develop PTS within two years, and the incidence of 10-year PTS is even as high as 70-90%. ②Non-traditional treatment can also be called thrombus removal therapy, which includes: surgical thrombectomy, mechanical thrombus removal, and catheter-directed thrombolysis (CDT). A multicenter, randomized, controlled clinical phase III trial comparing the efficacy of CDT with standard anticoagulation therapy started in the United States in late 2009 enrolled 692 patients with acute DVT in 30 clinical centers. The results of this clinical trial will be an important guide for future CDT treatment for patients with DVT. Therefore, CDT technology has become one of the most important tools for the treatment of DVT in the lower extremities today. Catheter thrombolysis can achieve 85-100% thrombus dissolution rate in the acute phase. However, with this technique alone, the vascular patency rate is still only 49-79% one year after surgery. The reason for this contrast may lie in iliac compression (IC), or Cockett’s syndrome, which is mainly due to the pulsatile compression of the left common iliac vein anteriorly by the right common iliac artery and the bony pushing of the posterior wall, with long-term wall thickening, intraluminal adhesions and lumen narrowing, resulting in obstruction of blood return to the left lower extremity when the iliac vein diameter stenosis When the stenosis of the iliac vein exceeds 50%, the distal vein of the stenosis is more prone to thrombosis, which is the reason why the compression of the iliac vein and secondary thrombosis are more likely to occur on the left side, and is also one of the important reasons for the recurrence of thrombosis or PTS after thrombosis. In 2005, Kwak et al. reviewed and analyzed the early and long-term efficacy of acute lower limb DVT with combined iliac vein lesions after treatment with combined CDT and stenting of the diseased iliac vein, and reported that the success rate of this technique was 96%, the patency rate was 100% at 1 year and 95% at 2 years after the operation; in China, it was reported that DVT with combined iliac vein stenosis was treated with CDT before iliac vein stenting. It is believed that catheter thrombolysis can effectively treat acute lower extremity DVT, and restoration of iliac vein patency is the key to maintain the medium and long-term efficacy of endovenous treatment. Comprehensive medical literature in the past decade shows that it is very necessary to treat lower extremity DVT with combined iliac vein lesions after performing CDT with simultaneous treatment of iliac vein lesions, which can reduce the recurrence of DVT and decrease the incidence of intermediate and long-term PTS. The “Guidelines for the diagnosis and treatment of deep vein thrombosis in China” (2011, 2nd edition) also clearly state that iliac vein stenosis or occlusion should be treated after recommended thrombus lysis. Nevertheless, these current bases are only single-center retrospective clinical data at home and abroad, and there is a lack of evidence from multicenter prospective studies. Prospective studies of large number of cases are needed in the future, so as to provide a stronger evidence-based medical basis for the standardized treatment of this disease.