A miniprobe has been applied to measure the ultrasonic attenuation coefficient for tissue mimicking phantoms, and freshly excised beef tissues. Some measuring errors by conventional probes might be minimized from adopting the miniprobe design. The miniprobe has the small transducer area as well as the function to measure the propagation path distance. Two methods to estimate the attenuation coefficient both from the time waveform and frequency spectra are discussed for our application in transmission mode. The methods and precision of the measurements were verified by eight tissue-mimicking phantoms before the approach to several beef tissues. The range of the errors of the measurement of the whole phantoms were within 0.77% to 1.71% calculated by power spectrum, and within 0.33% to 1.83% calculated by time domain. The results of measurement in phantoms confirm the successive measurement in tissues. According to the result of the attenuation coefficient estimated from phantoms and tissues, the estimation from the power spectrum is larger than that from the time waveform. The results of the errors indicate that directly measuring the heterogeneous materials in the time domain will cause more errors.