Objective:To analyze the correlation between the skin temperature changes in the radiation area and the occurrence of radiodermatitis during postoperative radiotherapy for female breast cancer and to explore the application value of skin temperature monitoring in the early warning of radiodermatitis risks.Methods:A total of 103 patients who received three-dimensional conformal radiotherapy after radical mastectomy in the Fourth Hospital of Hebei Medical University were continuously enrolled from May to November, 2022 in this study. Their skin temperature in the radiation area and radiodermatitis were recorded weekly. The relationships between relative skin temperature differences and different grades of radiodermatitis were determined. The optimal cut-off values for grade ≥ radiodermatitis were calculated, and the predictive effect was evaluated using the receiver operating characteristic (ROC) curve. Furthermore, the radiodermatitis risks under different skin temperatures were compared using binary logistic regression.Results:There was a positive correlation between the skin temperature in the radiation field and the grade of radiodermatitis. The optimal cut-off values for the average relative skin temperature difference of the chest wall (under 40 Gy/20 fractions), the maximum relative skin temperature difference of the chest wall (under 40 Gy/20 fractions), and the relative skin temperature difference of the supraclavicular block (under 30 Gy/15 fractions) were 0.45℃, 0.55℃, 0.15℃, respectively. The patients were divided into low- and high-risk groups based on the optimal cut-off values (0.45℃, 0.55℃, and 0.15℃). Binary logistic regression result showed that the risks of grade ≥ 2 radiodermatitis in the high-risk group were 5.71, 4.29, and 5.15 times those in the low-risk group, respectively ( OR = 5.71, 95% CI 1.81-17.99, P = 0.003; OR = 4.29, 95% CI 1.65-11.12, P = 0.003; OR = 5.15, 95% CI 2.16-12.31, P < 0.001). Conclusions:Skin temperature monitoring using medical infrared thermometers can be used to effectively predict the occurrence of grade ≥ 2 radiodermatitis. The skin temperature changes in the radiotherapy area should be closely observed. The risk of grade ≥ 2 radiodermatitis will increase when the mean and maximum relative temperature differences of the chest wall increase by 0.45℃ and 0.55℃, respectively under 40 Gy/20 fractions of radiotherapy or when the relative temperature differences of the supraclavicular block increases by 0.15℃ under 30 Gy/15 fractions of radiotherapy.