Abstract: Objective To evaluate the correlation between acute oral mucositis and dosimetric factors in intensity-modulated radiotherapy (IMRI) in locally advanced squamous cell carcinoma of hypopharynx and larynx (LA-SCCH/L). Methods From August 1, 2008 to December 31, 2014, 80 patients with LA-SCCH/L were treated by helical tomotherapy (HT) or RapidArc unit (RA), combined with concurrent cisplatin-based chemotherapy in our hospital. The related dosimetric factors were analyzed by receive operating characteristic (ROC) curve to detect the cutoff value of risk factors for the acute oral mucositis. Results No significant difference was found in the incidence of acute oral mucositis between HT and RA. Logistic analysis showed that oral V₃₀was independently associated with ≥ G2 mucositis (P=0.035) with a cut-off value of 42.4% detected by ROC analysis. The incidence of ≥ G2 oral mucositis was 75% (18/24) in patients with oral V₃₀ ≥ 42.4%, and it was only 35.7% in patients with oral V₃₀< 42.4% (20/56). Conclusion In the treatment of LA-SCCH/L, HT and RA are effective in protecting the normal tissues, without significant difference in acute oral mucositis. Oral V₃₀is related to acute oral mucositis.