Abstract: In this paper, a method named as the Difference Ratio Correction (DRC) Method is proposed to estimate the acoustical attenuation in vivo using the video output of commercial B-scanners. This method eliminated the affects of such factors as gains, the Time-Gain-Compensatin of the scanner, the diffraction and scattering of the beam of the probe, etc. Another advantage of the method is that it needn't modify the construction of the scanner, hence, it can be applied to clinical situations easily. In this paper, the formula used to calculate the attenuation slope of ultrasonic tissue mimicking phantoms measured by the DRC method is reported and compared with those from the transmission method. Experimental results support the effectiveness of the method.