The thickness, sound velocity and attenuation coefficient of a biological tissue were measured using combination with reflection and transmission method. The total attenuation of a tissue was measured by comparing the spectral of a ultrasonic pulse transmitted through it with the spectral of a standard pulse. On condition that a ultrasonic pulse beam is transmitted through the tissues having different sound velocity, the amplitude of the transmitted wave will become weak due to phase cancellation effect. In this paper, this phenomenon is analyzed and its simulation and experimental results are reported. Moreover the measure of occurrence of this apparent attenuation due to phase cancellation is discussed. As to the measuring system, because of using with a focused 20 MHz probe (beam width 0.1 mm), it is possible to measure the distribution of acoustic characteristics for a tissue with high resolution.