Abstract: Objective: To analyze the accuracy of the distance predicted between rectal cancer and the anal edge using rectal palpation and colonoscopy. Methods: Parallel analyses were conducted for 64 cases with rectal cancer to determine the preoperative distance between the tumor and the anal edge as measured by rectal palpation (designated as "T distance "), colonoscopy ("F distance ") and the postoperative excised specimen ("E distance"). The T distance measurements were divided into two groups: Group A consisted of 29 samples that had a T distance ≤ 4cm and Group B consisted of 35 samples that had a T distance between 4 cm and 7 cm. Results: There was no significant difference between the F and the E distance (P<0.01). In group A, there was no significant difference between the T and the E distance (P>0.01), but there was a significant difference between the T and the E distance in group B (P<0.01), with a linear correlation. The equation for correction adjusts the E distance to "T distance times 1.3-1". Conclusion: T distance is more accurate than F distance. T distance in group A is more accurate than that in group B. In group B, the calculation of E distance can be more accurate after applying the rectification formula.