Panax notoginseng saponins (PNS) have recently attracted great attention for their anti-cancer activity in colorectal cancer (CRC). The aim of this study was to explore the functional role and underlying mechanisms of PNS on CRC radiosensitivity. Cell viability was assessed by a Cell Counting kit-8 assay. Cell survival and apoptosis were determined using colony formation assay and flow cytometry, respectively. Quantitative real-time PCR was used to quantify the levels of SNHG6 and miR-137. The targeted correlation between SNHG6 and miR-137 was validated by dual-luciferase reporter and RNA immunoprecipitation assays. Our data supported that PNS weakened the viability of CRC cells. Moreover, PNS promoted the radiosensitivity of CRC cells. Mechanistically, PNS enhanced CRC cell radiosensitivity by upregulating SNHG6. SNHG6 directly targeted miR-137 and inhibited miR-137 expression. MiR-137 was involved in the regulatory effect of SNHG6 on CRC cell radiosensitivity. Furthermore, PNS increased miR-137 expression through SNHG6 in CRC cells. Our study suggested that PNS promoted radiosensitivity in CRC cells at least partly through regulating the SNHG6/miR-137 axis, providing a novel understanding of the anti-cancer mechanism of PNS in CRC.