Acute radiation‑induced esophagitis (ARIE) is a common complication of radiotherapy. The aim of this study was to clarify the molecular mechanism of pain relief by the compound of white peony root oral liquid (cWPROL) in ARIE. An animal model of ARIE was established and either cWPROL or a mixture of lidocaine, dexamethasone and gentamycin (mLDG) was administered. We indirectly observed rat symptoms of pain by recording the weight of food and the volume of water consumed by the rats, along with changes in body weight. Additionally, the expression levels of substance P (SP) in the esophageal tissues were detected by immunohistochemistry. It was demonstrated that cWPROL was able to release the pain of ARIE by decreasing the expression of SP; this may be one of the molecular mechanisms via which cWPROL induces pain relief.