In this paper, a thermal tomography method, which can deduce the temperature distribution of the inner heat source from the surface thermal map, is applied to the clinical breast diagnosis. With the comparison to the conventional mammography and ultrasound imaging, the clinical value of thermal tomography on breast diagnosis is discussed. Moreover, with the help of the infrared thermal imaging, the different rules of the temperature response on normal or cancerous mammary tissue by activating the sympathetic nervous system with a cold stimulus on hands is studied preliminarily.