Objective Dual-boundary echo comparison(DBEC)is a new method of measuring the blood ultrasonic attenuation coefficient(USAC)noninvasively. The correction coefficient of the transducer which reflects the beam shape needs to be determined before the DBEC is applied. The application of the correction coefficient in non-water medium which is obtained in water produces error. This paper studies the range and the influence factors of the error，the methods of minimizing the error. Methods The refractive index of agar phantom is equivalent to human tissues. We insert the agar phantom between the probe and the sample tube，then measure the correction coefficients and compare with those obtained in water. We also measure the USAC of castor oil before and after inserting the tissue-mimicking phantoms and compare the results. Results The experiments show that the maximum error of correction coefficient and the USAC of castor oil are both below 7% within the probe’s frequency bandwidth，however the relationship between the errors and the thickness of the inserted phantom is complicated. Conclusions It is suggest that correction coefficient should be measured in tissue-mimicking phantoms to minimize the error in DBEC.