Objective It is a thorny problem to reconstruct long ureteral defect in urinary surgery. To investigate the feasibil ity of intestinal sero-muscular segment with autograft of bladder mucosa as a replacement material for reconstructionof long ureteral defect. Methods Twelve adult Beagle dogs (weighing 6.5-9.3 kg and being male or female) were randomlydivided into 3 groups, each group including 4 dogs. In group A, lower segment of ureter was reconstructed by autograft of bladder mucosa to the intestinal sero-muscular segment; furthermore, the proximal and distal reconstructed ureter were anastomosed to the bladder and the upper ureter, respectively. In group B, upper segment of ureter was reconstructed by the same method as that of group A, the proximal and distal reconstructed ureter anastomosised with pelvic and lower ureter, respectively. In group C, whole ureter was reconstructed by the same method as that of group A, the proximal and distal reconstructed ureter were anastomosised with pelvic and bladder, respectively. Blood urea nitrogen, Cr2+, K+, Na+, Cl-, Ca2+ and carbon dioxide combining power were detected before operation, the general state, drainage volume, heal ing of wound, and compl ications were observed after operation. At 6 weeks, the blood biochemical indexes and intravenous urography (IVU) were detected, and the gross and histological observations of ureter were done. Results In group B, urine leakeage and infection occurred in 1 dog 2 days after operation because ureter stent prolapsed; other dogs had no complications. There was no significant difference in the biochemical indexes between before operation and 6 weeks after operation. IVU showed: in group A, hydronepherosis and ureterectasia occurred on the operation side of 1 dog; in group B, anastomotic stricture between the reconstructed ureter and lower ureter and hydronepherosis occurred in 1 dog; and in other dogs of all groups, renal function was good and the reconstructed ureter had peristalsis function. The histopathological observation showed that the reconstructed ureter had similar structure to normal ureterat 6 weeks in 3 groups; the inflammatory cells infiltrating of the reconstructed ureter was observed in 1 dog of groups A and C, respectively. Conclusion Reconstruction of ureter by intestinal sero-muscular segment with autograft of bladder mucosa has similar structure and function to the normal ureter. The results might provide an experimental basis for cl inical use.