Abstract: Objective To explore the effect of IR-780 combined with laser on breast cancer xenograft in mice. Methods 4T1 breast cancer cells were inoculated in the right subcutaneous abdomen of BALB／c mice to establish tumor models. Experimental mice were randomly divided into four groups（five mice for each group）： Control group（mice injected with 0.1 ml saline）， Laser group（mice irradiated with laser of 2.2 W／cm2 for 4 min）， IR-780 group（mice injected with 80 μg IR-780） and IR-780+Laser group（mice injected with 80 μg IR-780 following irradiation with laser of 2.2 W／cm2 for 4 min）. The tumor volume was measured and recorded. The ultrasonic echo of tumor tissue in each group was evaluated with Vevo 2100 high frequency system at 0， 12 and 6 h after treatment， respectively. The apoptotic index of tumor tissue in each group was detected with TUNEL at 60 h after treatment. Results Compared with other three groups， the tumor volume of IR-780+Laser group was significantly decreased at 60 h after treatment（P＜0.05）. There were lower gray scale values of ultrasonic echo in IR-780+Laser group at 12 and 60 h versus 0 h after treatment（P＜0.05）. The gray scale values of ultrasonic echo in IR-780+Laser group were also lower than other three groups（P＜0.05）. There were higher apoptotic index of IR-780+Laser group versus other three groups（P＜0.05）. No significant difference was observed on the tumor volume， gray scale value of ultrasonic echo and apoptotic index among Control group， Laser group and IR-780 group（P＞0.05）. Conclusion The obvious suppressive effect was observed in photothermal therapy with IR-780 on breast cancer tumor， evidenced by change of ultrasonic echo of tumor tissue in high frequency and increased apoptosis.