Abstract: Objective: To explore the apoptosis of endothelial cells after acute deep venous thrombosis in rabbit and its significanse in the pathological processes. Methods: Fifty-five adult rabbits were randomly divided into the normal group (n=5) in which the samples were gotten directly, the thrombosis group (TB, n=25) caused by ligating a sect of the posterior vena cava under renal vein to induce thrombosis model, the sham operation group (SH, n=25) that were simply belly open and close to be used as controls. In different periods after acute deep venous thrombosis, morphological change of the endothelial cell apoptosis on target vessels was observed by means of transmission electron microscopy. In situ end-labeling of DNA fragments (TUNEL) was used to detect the endothelial cell apoptosis. Bax and bcl-2 proteins expressed by endothelial cells were determined with immunohistochemical staining. Results: Venous thrombosis models were successfully obtained in all cases. Transmission electron microscopy results showed that apoptosis of partial endothelial cells on target vessels on the 1st day, the 2nd day and the 4th day. TUNEL-positive cell rate reached the maximum on the first day, the second day and there was no significant difference between the two groups (P>0.05), and decreased gradually on the 4th day and the 7th day in TB group. There was significant difference between TB group and SH group respective time (P<0.05-P<0.01). Expression of bcl-2 protein in TB group was increased gradually with the days passing by while bax protein reached the peak on 2nd days and decreased gradually 4th day, 7th day, there was marked difference between TB group and SH group at different time (P<0.05-P<0.01). Conclusions: The apoptosis of the endothelial cells after acute deep venous thrombosis occurs, reaches the peak on the first and the second day and decreases gradually after 2nd days. The bcl-2 and bax participate in the regulation and control of the apoptosis of the endothelial cells.