Conventional ultrasonic B-mode images qualitatively describe tissue structures,but they are unsuitable for quantitative analyses of scatterer properties. Recent studies have developed an ultrasonic parmetric imaging technique based on the Nakagarmi statistical distribution,and its ability to quantify scatterer concentrations has been confirmed The aim of the present study was to further explore the performances of the Nakagami image under conditions of different signal-to-noise ratios (SNRs). Experiments on a tissue-mimicking phantom were carried out. The results show that the noise effect degraded the performance of the Nakagami image in tissue characterization. When the signal SNR decreased by 8 dB,the contrast-to-noise ratio (CNR) of the Nakagami image for the hyperechoic region decreased by 27%， and that of the hypoechoic one decreased by 80%. These results indicate that the Nakagami image behaves well in identifying regions with high scatterer concentrations but does not perform well when both the scatterer concentration and SNR are low.