Intersphincteric resection (ISR), as an ultra-low sphincter-preserving operation, is widely used in clinical practice at present. ISR can allow some patients with very low rectal cancer to avoid the pain of anal resection while ensuring oncological efficacy. However, the procedure of ISR requires wider intersphincteric dissection which may cause nerve damage, and the removal of partial or total internal anal sphincter as an "inherent defect" of ISR can result in poor anal function postoperatively. Based on the in-depth understanding of regional anatomy and physiological function, the author proposed a new functional sphincter preservation operation for very low rectal cancer—conformal sphincter preservation operation (CSPO) which has achieved good outcome in clinical practice. This article will revisit the brief history of rectal cancer surgery and discuss the main mechanisms underlining the poor anal function after ISR. Based on the anatomical study of the pelvic floor and anal canal, CSPO can improve the postoperative anal function of very low rectal cancer patients by reducing the damage of the autonomic nerves, receptor corpuscles and muscle fibers in the intersphincteric space, retaining more dentate line and internal sphincter with the design of resection line of tumor lower border under direct vision, and elevating the anastomosis height. At the same time, the future treatment prospect of low rectal cancer is envisioned.