Abstract:  In order to ensure the efficacy of ultrasound hyperthermia and HIFU, it is needed to control the temperature，therefore the temperature measurement in the treatment is necessary.Thermocouple is often used in clinical hyperthermia. Although it is a high accurate technique, it is needed to insert into
the organ, which gives the patient pain, and therefore is not widely used.This non-destructive temperature measurement methods have been proposed，such as electrical impedance tomography, X-CT, MRI imaging, ultrasound，microwave hot temperature compensation method and computer simulation
in which a computer simulation of temperature field is based on the Pennes bio-heat equation, considering the blood flow, the ultrasonic source strength and the measured temperature outside the skin. Because the biological tissues are multi-layer structures and their shapes are irregular, therefore the numerical
method must be used to obtain the temperature field distribution, In this paper, firstly, Khokhlov- Zabolotaskaya-Kuznetsov (KZK) equation is used to get the sound field distribution of multi-layer tissue，a finite clement software is used to calculate the Pennes equation, and axial-temperature distribution for
multi-layer tissues is obtained under different conditions.The experimental results are compared with theoretical prediction and show that the experiments fit the theoretical results well. When the thickness of samples increase,a part of energy is absorbed by the anterior part of tissue compared with before，so
the focus will get less energy, and the maximum temperature elevation will decrease，and the position of maximum temperature will also move backward. When the sound pressure at the surface of the transducer increase the maximum temperature elevation of the sample will also increase but the position
of maximum temperature remain same,therefore, the sound pressure at the surface of the transducer has a great influence on the temperature field. When the samples move backward，less energy will be absorbed by the anterior part of tissue, so the focus will get more energy, and the maximum temperature
elevation will increase,and the position of maximum temperature will also move forward. For two-layer tissue(fat- liver) and threrlaycr tissue(fat-muscle-liver)，a part of energy is absorbed by fat sample and muscle sample，less energy will be absorbed at the focus, and themaximum temperature elevation will
decrease, and the position of maximum temperature will also move backward. Our research show that the influence of the thickness and tissue parameters are very important to the hyperthermia,they must be taken into consideration during the hyperthermia with ultrasound. We hope our study can provide some useful information for the hyperthermia.