Objective To investigate filtration efficiency of convertible vena cava filters on treating pulmonary embolism under the condition of different thrombus diameter and content. Methods Three kinds of convertible vena cava filter models with different filtering unit structures (L-style, S-style, W-style) were constructed to numerically simulate hemodynamics based on computational fluid dynamic (CFD) methods, and their filtration efficiency were comparatively analyzed under the condition of different thrombus diameter (5, 10, 15 mm) and content (10%, 15%, 20%). Results With the increasing of thrombus diameter and content, the volume fraction of thrombus distributed on the filter bars increased and filtration efficiency of the filter became better. When the thrombus diameter was 5 mm, the S-style filter’s filtration efficiency was the best as compared with the other two styles of filters. When the thrombus diameter was 10 mm, the W-style filter showed the best filtration efficiency. When the thrombus diameter was 15 mm, the S-style and W-style filter showed the same filtration efficiency, which was better than the L-style filter. Conclusions The implantation of vena cava filters will cause hemodynamic changes, and its filtration efficiency is not only related to filtering unit structures, but also closely related to the diameter and content of thrombus. These results provide a theoretical reference basis for the design and clinical choice of the novel convertible vena cava filter.