Firstly, to dissect the retroperitoneaum along transitional zone between mesocolon and retroperitoneum, and to separate the mesentery to the root of the inferior mesenteric artery and to dissect 253 group lymph nodes, then to clamp and cut inferior mesenteric vessels 1 cm away from abdominal aorta. Sencondly, to separate mesocolon from medial to lateral to the paracolic sulcus, and to dissect retroperitoneum on the left side for the sufficient mobilization of descending colon and sigmoid colon. Thirdly, to dissect rectal mesentery sharply between proper fascia of rectum and pelvic fascia according to TME principle, from posterior wall to lateral and anterior wall then to pelvic floor. To clamp rectum 2 cm below tumor, and to rinse the distal rectum before cutting it with a stapler. Finally, to make an arc incision around the umbilicus, then to pull out the proximal intestine and to cut colon 15 cm away from the tumor. To place in the anvil of the circular stapler in proximal intestine, and to put it back into abdomen and to rebuild artificial pneumoperitoneum. Then to achieve transanal anastomosis by using circular stapler. then to rinse the abdomen and to put the drainage tube after surgery.