Objective:To design and evaluate a novel arcuate multi-channel rectal endoluminal applicator to enhance dose coverage of tumors in the upper and middle rectum and reduce pressure on the rectal wall.Methods:Pelvic MRI images of 200 Chinese cases without rectal lesions in the Peking University Third Hospital from July 2022 to August 2022 were retrospectively analyzed. Based on the image data, a rectal model with general characteristics of the population and two novel hard and soft rectal endoluminal applicators were designed and fabricated. The following properties of the conventional applicators and two new applicators were compared: deformation to the model rectal wall, maximum pressure, stable pressure, D 90%, D 100%, V 100%, V 150% and V 200% of the GTV, and D 2 cm3, D 1 cm3, and D 0.1 cm3 of the organs at risk (OAR). ANOVA or Kruskal-Wallis H-test was used to compare the differences among three applicators, and Dunnett's multiple comparison test was used for pairwise comparisons. Results:The novel hard and soft rectal endoluminal applicators caused less deformation of the model rectal wall. The maximum pressure on the rectal wall was (0.606 ± 0.182) kPa and (0.481 ± 0.229) kPa for the hard arcuate applicator and soft arcuate applicator, respectively, and the stable pressure was (0.207 ± 0.137) kPa and (0.055 ± 0.097) kPa, respectively, which were significantly smaller than those of the conventional applicator ( P <0.001, <0.001; P =0.024, <0.001), and the degree of reduction was at or near 50%. Under the premise of ensuring target dose, the D 2 cm3, D 1 cm3, and D 0.1 cm3 of OAR in the treatment plan designed with the novel applicator were significantly reduced compared to the cylindrical applicator (all P<0.001). Conclusion:The novel arcuate multi-channel rectal endoluminal applicator can significantly reduce rectal wall pressure and deformation, while also reducing the dose to OAR without compromising target dose coverage, offering certain therapeutic advantages.