Abstract: Low intensity ultrasound can reduce the systemic dose and reverse the drug resistance by enhancing the antitumor effect of the chemotherapeutic drugs and overcoming tumor resistance to chemotherapy， as well as increasing the targeting of chemotherapy. In recent years， oncologists pay more attention to the researches about the enhancement of antitumor effect induced by low intensity ultrasound. This article reviews the biological effect of ultrasound，the chemosensitizing effect and its mechanism induced by low intensity ultrasound.