Purpose: To evaluate the mechanism for enhancing cell death induced by microwave ablation (MWA) combined with doxorubicin treatment in breast cancer cells. Materials and methods: Different temperatures of heat treatment were used to mimic the tumor affected by sublethal heat during MWA in vitro. Breast cancer cells were treated at 43 °C and 45 °C, with or without doxorubicin. Cell viability, apoptosis, and intracellular reactive oxygen species (ROS) were evaluated in MDA-MB-231 and SUM-1315 cells. Nude mice breast cancer models were randomly divided into control, MWA, doxorubicin, and combined treatment groups. Tumor apoptosis and DNA damage were evaluated in these groups. Results: The combined group had lower cell viability than the heat or doxorubicin group (all P < 0.05), and enhanced apoptosis rate was observed in the combined group compared to others (all P < 0.01) in MDA-MB-231 and SUM-1315. Increased capase3 (all P < 0.01) and decreased Bcl-Xl (all P < 0.01) were detected after combined therapy compared to single treated group in vitro. The raisedCaspase3 and DNA damage marker histone H2A.X induced by combined treatment were also approved in the nude mice models. Combined treatment promoted ROS generation compared to doxorubicin or MWA treatment (all P < 0.01). NF-κB expression in the combined group was higher than that of the single treatment group (all P < 0.05). N-acetylcysteine (NAC), a ROS scavenger, partly restrained the combined treatment induced cell proliferation inhibition, Caspase3 and NF-κB compared to doxorubicin treatment (all P < 0.05). Conclusion: MWA combined with doxorubicin promote cell death via ROS induced cell apoptosis and DNA damage. Increasing ROS has potential for improving the efficiency of combined treatment.