The study was designed as a double-blind randomized controlled trial, with research assessors and patients intended to be blind to the intervention status. The staff members performing the assessment were not involved in implementing any aspect of the intervention. 108 patients were randomized to accept curving introducer Günther Tulip Filter and transcatheter thrombolysis or straight introducer Günther Tulip Filter and transcatheter thrombolysis. The assessments include the tilting angle between the axes of inferior vena cava and Günther Tulip Filter after implantation; the tilting angle between the axes of inferior vena cava and Günther Tulip Filter before retrieval; the fluoroscopy time of Günther Tulip Filter retrieval; the rate of retrieval hook adhering vascular wall; the success rate of retrieval.