Objective To investigate the effect of low-frequency pulse therapeutic instrument combined with thunder-fire moxibustion on postpartum breast pain. Methods A total of 78 patients with postpartum breast pain were selected as the study objects, and randomly divided into control group and observation group, with 39 cases in each group. The control group was treated with low-frequency pulse therapeutic instrument, while the observation group was treated with low-frequency pulse therapeutic instrument combined with thunder-fire moxibustion. The degree of breast distending pain, breast-feeding self-efficacy, breast swelling hardness, lactation volume, treatment effect, occurrence of complications and uterine recovery were compared between the two groups. Results Compared with before treatment, after 3 days of treatment, the score for the degree of breast distending pain in both groups decreased, which was lower in the observation group than that in the control group; the score of Breast‑Feeding Self‑Efficacy Scale (BSES-SF) in both groups increased, which was higher in the observation group than that in the control group; the height of fundus uteri in both groups decreased, which was lower in the observation group than that in the control group. After treatment, the breast swelling hardness and lactation volume of the observation group were better than those of the control group, the height of fundus uteri was lower than that of the control group, the lochia time was shorter than that of the control group, the incidence of complications was lower than that of the control group, the index of fundus uteri declining and the total effective rate of treatment were higher than those of the control group, with statistically significant differences (all P<0.05). Conclusion The application of low-frequency pulse therapeutic instrument combined with thunder-fire moxibustion in the treatment of postpartum breast swelling and pain can improve the effective rate of treatment, improve breast swelling and pain, promote lactation and uterine recovery, reduce postpartum complications, and enhance breast-feeding self-efficacy.